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	$198.69	10.777%	$220.1028	$220.10	$220.10	$220.10
Purchase #2	$85.34	4.736%	$89.3817	$89.38	$89.40	$89.40
Purchase #3	$233.50	4.558%	$244.1429	$244.14	$244.15	$244.10
Purchase #4	$187.87	4.170%	$195.7042	$195.70	$195.70	$195.70
Purchase #5	$20.49	6.460%	$21.8137	$21.81	$21.80	$21.80
Purchase #6	$99.69	4.232%	$103.9089	$103.91	$103.90	$103.90
Purchase #7	$224.52	10.680%	$248.4987	$248.50	$248.50	$248.50
7 purchase totals =	$1,050.10		$1,123.5529	$1,123.54	$1,123.55	$1,123.50