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	$56.88	4.498%	$59.4385	$59.44	$59.45	$59.40
Purchase #2	$240.93	10.171%	$265.435	$265.44	$265.45	$265.40
Purchase #3	$217.58	8.799%	$236.7249	$236.72	$236.70	$236.70
Purchase #4	$91.57	6.208%	$97.2547	$97.25	$97.25	$97.30
Purchase #5	$152.77	12.343%	$171.6264	$171.63	$171.65	$171.60
Purchase #6	$145.77	11.678%	$162.793	$162.79	$162.80	$162.80
Purchase #7	$206.76	11.162%	$229.8386	$229.84	$229.85	$229.80
7 purchase totals =	$1,112.26		$1,223.1111	$1,223.11	$1,223.15	$1,223.00