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	$171.68	4.482%	$179.3747	$179.37	$179.35	$179.40
Purchase #2	$208.60	5.129%	$219.2991	$219.30	$219.30	$219.30
Purchase #3	$61.75	4.309%	$64.4108	$64.41	$64.40	$64.40
Purchase #4	$190.67	7.348%	$204.6804	$204.68	$204.70	$204.70
Purchase #5	$34.61	3.142%	$35.6974	$35.70	$35.70	$35.70
Purchase #6	$116.83	9.157%	$127.5281	$127.53	$127.55	$127.50
Purchase #7	$152.37	12.381%	$171.2349	$171.23	$171.25	$171.20
7 purchase totals =	$936.51		$1,002.2254	$1,002.22	$1,002.25	$1,002.20