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	$100.72	4.200%	$104.9502	$104.95	$104.95	$105.00
Purchase #2	$65.55	10.289%	$72.2944	$72.29	$72.30	$72.30
Purchase #3	$224.61	9.292%	$245.4808	$245.48	$245.50	$245.50
Purchase #4	$214.50	13.453%	$243.3567	$243.36	$243.35	$243.40
Purchase #5	$176.62	4.332%	$184.2712	$184.27	$184.25	$184.30
Purchase #6	$38.56	13.142%	$43.6276	$43.63	$43.65	$43.60
Purchase #7	$74.64	4.830%	$78.2451	$78.25	$78.25	$78.20
7 purchase totals =	$895.20		$972.2260	$972.23	$972.25	$972.30