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	$186.53	13.176%	$211.1072	$211.11	$211.10	$211.10
Purchase #2	$137.94	10.385%	$152.2651	$152.27	$152.25	$152.30
Purchase #3	$149.79	12.850%	$169.038	$169.04	$169.05	$169.00
Purchase #4	$53.85	9.498%	$58.9647	$58.96	$58.95	$59.00
Purchase #5	$160.83	3.490%	$166.443	$166.44	$166.45	$166.40
Purchase #6	$131.27	8.770%	$142.7824	$142.78	$142.80	$142.80
Purchase #7	$250.67	7.140%	$268.5678	$268.57	$268.55	$268.60
7 purchase totals =	$1,070.88		$1,169.1682	$1,169.17	$1,169.15	$1,169.20