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	$55.76	9.719%	$61.1793	$61.18	$61.20	$61.20
Purchase #2	$185.59	6.203%	$197.1021	$197.10	$197.10	$197.10
Purchase #3	$160.97	12.275%	$180.7291	$180.73	$180.75	$180.70
Purchase #4	$64.72	4.266%	$67.481	$67.48	$67.50	$67.50
Purchase #5	$174.72	12.247%	$196.118	$196.12	$196.10	$196.10
Purchase #6	$151.52	6.848%	$161.8961	$161.90	$161.90	$161.90
Purchase #7	$86.47	11.737%	$96.619	$96.62	$96.60	$96.60
7 purchase totals =	$879.75		$961.1246	$961.13	$961.15	$961.10