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	$162.69	7.661%	$175.1537	$175.15	$175.15	$175.20
Purchase #2	$80.60	10.581%	$89.1283	$89.13	$89.15	$89.10
Purchase #3	$119.66	3.570%	$123.9319	$123.93	$123.95	$123.90
Purchase #4	$96.81	12.364%	$108.7796	$108.78	$108.80	$108.80
Purchase #5	$246.31	5.181%	$259.0713	$259.07	$259.05	$259.10
Purchase #6	$240.87	7.120%	$258.0199	$258.02	$258.00	$258.00
Purchase #7	$232.59	7.592%	$250.2482	$250.25	$250.25	$250.20
7 purchase totals =	$1,179.53		$1,264.3329	$1,264.33	$1,264.35	$1,264.30