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	$189.54	5.607%	$200.1675	$200.17	$200.15	$200.20
Purchase #2	$84.90	5.349%	$89.4413	$89.44	$89.45	$89.40
Purchase #3	$17.64	10.162%	$19.4326	$19.43	$19.45	$19.40
Purchase #4	$236.78	10.872%	$262.5227	$262.52	$262.50	$262.50
Purchase #5	$69.67	12.614%	$78.4582	$78.46	$78.45	$78.50
Purchase #6	$231.44	4.740%	$242.4103	$242.41	$242.40	$242.40
Purchase #7	$44.68	11.746%	$49.9281	$49.93	$49.95	$49.90
7 purchase totals =	$874.65		$942.3607	$942.36	$942.35	$942.30