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	$56.76	4.197%	$59.1422	$59.14	$59.15	$59.10
Purchase #2	$31.90	3.519%	$33.0226	$33.02	$33.00	$33.00
Purchase #3	$147.34	6.248%	$156.5458	$156.55	$156.55	$156.50
Purchase #4	$156.33	11.498%	$174.3048	$174.30	$174.30	$174.30
Purchase #5	$10.40	12.348%	$11.6842	$11.68	$11.70	$11.70
Purchase #6	$167.92	13.329%	$190.3021	$190.30	$190.30	$190.30
Purchase #7	$26.63	9.132%	$29.0619	$29.06	$29.05	$29.10
7 purchase totals =	$597.28		$654.0636	$654.05	$654.05	$654.00