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	$6.74	4.599%	$7.05	$7.05	$7.05	$7.10
Purchase #2	$97.54	8.791%	$106.1147	$106.11	$106.10	$106.10
Purchase #3	$215.83	5.151%	$226.9474	$226.95	$226.95	$226.90
Purchase #4	$63.36	6.251%	$67.3206	$67.32	$67.30	$67.30
Purchase #5	$99.72	9.426%	$109.1196	$109.12	$109.10	$109.10
Purchase #6	$170.69	12.640%	$192.2652	$192.27	$192.25	$192.30
Purchase #7	$73.39	7.325%	$78.7658	$78.77	$78.75	$78.80
7 purchase totals =	$727.27		$787.5833	$787.59	$787.50	$787.60