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	$127.98	3.497%	$132.4555	$132.46	$132.45	$132.50
Purchase #2	$104.98	13.543%	$119.1974	$119.20	$119.20	$119.20
Purchase #3	$86.83	10.544%	$95.9854	$95.99	$96.00	$96.00
Purchase #4	$98.87	11.421%	$110.1619	$110.16	$110.15	$110.20
Purchase #5	$115.87	13.545%	$131.5646	$131.56	$131.55	$131.60
Purchase #6	$58.74	4.650%	$61.4714	$61.47	$61.45	$61.50
Purchase #7	$53.73	10.868%	$59.5694	$59.57	$59.55	$59.60
7 purchase totals =	$647.00		$710.4056	$710.41	$710.35	$710.60