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	$72.73	13.206%	$82.3347	$82.33	$82.35	$82.30
Purchase #2	$241.75	7.188%	$259.127	$259.13	$259.15	$259.10
Purchase #3	$209.68	7.486%	$225.3766	$225.38	$225.40	$225.40
Purchase #4	$19.36	12.333%	$21.7477	$21.75	$21.75	$21.70
Purchase #5	$228.30	9.180%	$249.2579	$249.26	$249.25	$249.30
Purchase #6	$56.61	5.197%	$59.552	$59.55	$59.55	$59.60
Purchase #7	$181.76	4.496%	$189.9319	$189.93	$189.95	$189.90
7 purchase totals =	$1,010.19		$1,087.3278	$1,087.33	$1,087.40	$1,087.30