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	$121.32	7.194%	$130.0478	$130.05	$130.05	$130.00
Purchase #2	$184.94	6.163%	$196.3379	$196.34	$196.35	$196.30
Purchase #3	$243.41	5.437%	$256.6442	$256.64	$256.65	$256.60
Purchase #4	$247.98	13.374%	$281.1448	$281.14	$281.15	$281.10
Purchase #5	$192.83	3.359%	$199.3072	$199.31	$199.30	$199.30
Purchase #6	$57.36	13.517%	$65.1134	$65.11	$65.10	$65.10
Purchase #7	$99.88	10.436%	$110.3035	$110.30	$110.30	$110.30
7 purchase totals =	$1,147.72		$1,238.8988	$1,238.89	$1,238.90	$1,238.70