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	$101.38	11.634%	$113.1745	$113.17	$113.15	$113.20
Purchase #2	$81.89	9.263%	$89.4755	$89.48	$89.50	$89.50
Purchase #3	$102.50	13.351%	$116.1848	$116.18	$116.20	$116.20
Purchase #4	$182.71	9.626%	$200.2977	$200.30	$200.30	$200.30
Purchase #5	$105.98	5.829%	$112.1576	$112.16	$112.15	$112.20
Purchase #6	$102.87	8.221%	$111.3269	$111.33	$111.35	$111.30
Purchase #7	$28.44	12.154%	$31.8966	$31.90	$31.90	$31.90
7 purchase totals =	$705.77		$774.5136	$774.52	$774.55	$774.60