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	$52.91	8.796%	$57.564	$57.56	$57.55	$57.60
Purchase #2	$7.57	3.365%	$7.8247	$7.82	$7.80	$7.80
Purchase #3	$126.56	5.179%	$133.1145	$133.11	$133.10	$133.10
Purchase #4	$114.28	13.762%	$130.0072	$130.01	$130.00	$130.00
Purchase #5	$138.40	5.492%	$146.0009	$146.00	$146.00	$146.00
Purchase #6	$48.36	10.542%	$53.4581	$53.46	$53.45	$53.50
Purchase #7	$42.61	4.242%	$44.4175	$44.42	$44.40	$44.40
7 purchase totals =	$530.69		$572.3869	$572.38	$572.30	$572.40