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	$54.76	7.740%	$58.9984	$59.00	$59.00	$59.00
Purchase #2	$176.54	8.517%	$191.5759	$191.58	$191.60	$191.60
Purchase #3	$190.68	3.374%	$197.1135	$197.11	$197.10	$197.10
Purchase #4	$238.45	3.860%	$247.6542	$247.65	$247.65	$247.70
Purchase #5	$73.95	5.553%	$78.0564	$78.06	$78.05	$78.10
Purchase #6	$72.72	11.858%	$81.3431	$81.34	$81.35	$81.30
Purchase #7	$137.73	7.706%	$148.3435	$148.34	$148.35	$148.30
7 purchase totals =	$944.83		$1,003.0850	$1,003.08	$1,003.10	$1,003.10