Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$103.31	4.819%	$108.2885	$108.29	$108.30	$108.30
Purchase #2	$155.81	5.662%	$164.632	$164.63	$164.65	$164.60
Purchase #3	$97.74	13.499%	$110.9339	$110.93	$110.95	$110.90
Purchase #4	$156.48	10.152%	$172.3658	$172.37	$172.35	$172.40
Purchase #5	$146.41	6.608%	$156.0848	$156.08	$156.10	$156.10
Purchase #6	$206.76	11.260%	$230.0412	$230.04	$230.05	$230.00
Purchase #7	$179.83	5.120%	$189.0373	$189.04	$189.05	$189.00
7 purchase totals =	$1,046.34		$1,131.3835	$1,131.38	$1,131.45	$1,131.30