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	$156.69	9.359%	$171.3546	$171.35	$171.35	$171.40
Purchase #2	$76.55	11.563%	$85.4015	$85.40	$85.40	$85.40
Purchase #3	$115.92	13.316%	$131.3559	$131.36	$131.35	$131.40
Purchase #4	$130.95	10.506%	$144.7076	$144.71	$144.70	$144.70
Purchase #5	$153.30	6.579%	$163.3856	$163.39	$163.40	$163.40
Purchase #6	$199.33	11.362%	$221.9779	$221.98	$222.00	$222.00
Purchase #7	$104.41	13.152%	$118.142	$118.14	$118.15	$118.10
7 purchase totals =	$937.15		$1,036.3251	$1,036.33	$1,036.35	$1,036.40