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	$162.54	11.664%	$181.4987	$181.50	$181.50	$181.50
Purchase #2	$202.75	6.804%	$216.5451	$216.55	$216.55	$216.50
Purchase #3	$140.37	13.487%	$159.3017	$159.30	$159.30	$159.30
Purchase #4	$176.78	11.342%	$196.8304	$196.83	$196.85	$196.80
Purchase #5	$234.45	4.450%	$244.883	$244.88	$244.90	$244.90
Purchase #6	$26.73	12.866%	$30.1691	$30.17	$30.15	$30.20
Purchase #7	$29.61	8.416%	$32.102	$32.10	$32.10	$32.10
7 purchase totals =	$973.23		$1,061.3300	$1,061.33	$1,061.35	$1,061.30