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	$213.75	7.310%	$229.3751	$229.38	$229.40	$229.40
Purchase #2	$109.56	4.181%	$114.1407	$114.14	$114.15	$114.10
Purchase #3	$123.41	9.301%	$134.8884	$134.89	$134.90	$134.90
Purchase #4	$53.67	13.658%	$61.0002	$61.00	$61.00	$61.00
Purchase #5	$34.98	8.483%	$37.9474	$37.95	$37.95	$37.90
Purchase #6	$39.83	8.373%	$43.165	$43.17	$43.15	$43.20
Purchase #7	$98.81	10.720%	$109.4024	$109.40	$109.40	$109.40
7 purchase totals =	$674.01		$729.9192	$729.93	$729.95	$729.90