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	$137.69	10.646%	$152.3485	$152.35	$152.35	$152.30
Purchase #2	$205.65	8.503%	$223.1364	$223.14	$223.15	$223.10
Purchase #3	$89.57	11.230%	$99.6287	$99.63	$99.65	$99.60
Purchase #4	$109.72	13.690%	$124.7407	$124.74	$124.75	$124.70
Purchase #5	$104.31	6.326%	$110.9087	$110.91	$110.90	$110.90
Purchase #6	$181.62	10.534%	$200.7519	$200.75	$200.75	$200.80
Purchase #7	$215.62	8.314%	$233.5466	$233.55	$233.55	$233.50
7 purchase totals =	$1,044.18		$1,145.0615	$1,145.07	$1,145.10	$1,144.90