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	$152.88	3.468%	$158.1819	$158.18	$158.20	$158.20
Purchase #2	$8.54	12.731%	$9.6272	$9.63	$9.65	$9.60
Purchase #3	$231.73	9.777%	$254.3862	$254.39	$254.40	$254.40
Purchase #4	$101.41	9.703%	$111.2498	$111.25	$111.25	$111.20
Purchase #5	$83.33	7.473%	$89.5573	$89.56	$89.55	$89.60
Purchase #6	$222.87	7.140%	$238.7829	$238.78	$238.80	$238.80
Purchase #7	$147.91	7.296%	$158.7015	$158.70	$158.70	$158.70
7 purchase totals =	$948.67		$1,020.4868	$1,020.49	$1,020.55	$1,020.50