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	$85.41	4.406%	$89.1732	$89.17	$89.15	$89.20
Purchase #2	$86.56	13.218%	$98.0015	$98.00	$98.00	$98.00
Purchase #3	$111.77	12.544%	$125.7904	$125.79	$125.80	$125.80
Purchase #4	$140.61	12.457%	$158.1258	$158.13	$158.15	$158.10
Purchase #5	$6.55	13.582%	$7.4396	$7.44	$7.45	$7.40
Purchase #6	$95.31	10.453%	$105.2728	$105.27	$105.25	$105.30
Purchase #7	$104.82	3.331%	$108.3116	$108.31	$108.30	$108.30
7 purchase totals =	$631.03		$692.1149	$692.11	$692.10	$692.10