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	$234.62	9.135%	$256.0525	$256.05	$256.05	$256.10
Purchase #2	$17.49	7.150%	$18.7405	$18.74	$18.75	$18.70
Purchase #3	$155.92	4.581%	$163.0627	$163.06	$163.05	$163.10
Purchase #4	$195.45	11.797%	$218.5072	$218.51	$218.50	$218.50
Purchase #5	$72.49	13.766%	$82.469	$82.47	$82.45	$82.50
Purchase #6	$160.46	8.347%	$173.8536	$173.85	$173.85	$173.90
Purchase #7	$79.48	12.840%	$89.6852	$89.69	$89.70	$89.70
7 purchase totals =	$915.91		$1,002.3707	$1,002.37	$1,002.35	$1,002.50