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	$96.51	3.558%	$99.9438	$99.94	$99.95	$99.90
Purchase #2	$221.69	3.637%	$229.7529	$229.75	$229.75	$229.80
Purchase #3	$92.29	12.819%	$104.1207	$104.12	$104.10	$104.10
Purchase #4	$6.40	11.593%	$7.142	$7.14	$7.15	$7.10
Purchase #5	$98.94	10.251%	$109.0823	$109.08	$109.10	$109.10
Purchase #6	$76.56	9.297%	$83.6778	$83.68	$83.70	$83.70
Purchase #7	$143.94	3.444%	$148.8973	$148.90	$148.90	$148.90
7 purchase totals =	$736.33		$782.6168	$782.61	$782.65	$782.60