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	$31.95	4.401%	$33.3561	$33.36	$33.35	$33.40
Purchase #2	$55.52	10.673%	$61.4456	$61.45	$61.45	$61.40
Purchase #3	$245.55	7.458%	$263.8631	$263.86	$263.85	$263.90
Purchase #4	$111.37	13.228%	$126.102	$126.10	$126.10	$126.10
Purchase #5	$57.73	6.649%	$61.5685	$61.57	$61.55	$61.60
Purchase #6	$87.33	5.232%	$91.8991	$91.90	$91.90	$91.90
Purchase #7	$109.71	13.524%	$124.5472	$124.55	$124.55	$124.50
7 purchase totals =	$699.16		$762.7816	$762.79	$762.75	$762.80