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	$174.50	3.600%	$180.782	$180.78	$180.80	$180.80
Purchase #2	$244.36	4.517%	$255.3977	$255.40	$255.40	$255.40
Purchase #3	$248.54	4.329%	$259.2993	$259.30	$259.30	$259.30
Purchase #4	$194.67	12.515%	$219.033	$219.03	$219.05	$219.00
Purchase #5	$220.53	13.550%	$250.4118	$250.41	$250.40	$250.40
Purchase #6	$119.93	3.300%	$123.8877	$123.89	$123.90	$123.90
Purchase #7	$240.41	12.369%	$270.1463	$270.15	$270.15	$270.10
7 purchase totals =	$1,442.94		$1,558.9578	$1,558.96	$1,559.00	$1,558.90