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	$89.45	8.864%	$97.3788	$97.38	$97.40	$97.40
Purchase #2	$233.75	6.463%	$248.8573	$248.86	$248.85	$248.90
Purchase #3	$108.49	3.155%	$111.9129	$111.91	$111.90	$111.90
Purchase #4	$53.74	10.762%	$59.5235	$59.52	$59.50	$59.50
Purchase #5	$234.90	4.868%	$246.3349	$246.33	$246.35	$246.30
Purchase #6	$175.47	11.524%	$195.6912	$195.69	$195.70	$195.70
Purchase #7	$190.50	12.107%	$213.5638	$213.56	$213.55	$213.60
7 purchase totals =	$1,086.30		$1,173.2624	$1,173.25	$1,173.25	$1,173.30