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	$193.83	11.683%	$216.4752	$216.48	$216.50	$216.50
Purchase #2	$157.34	5.616%	$166.1762	$166.18	$166.20	$166.20
Purchase #3	$33.40	12.857%	$37.6942	$37.69	$37.70	$37.70
Purchase #4	$209.82	9.368%	$229.4759	$229.48	$229.50	$229.50
Purchase #5	$86.59	9.631%	$94.9295	$94.93	$94.95	$94.90
Purchase #6	$90.36	6.404%	$96.1467	$96.15	$96.15	$96.10
Purchase #7	$20.93	13.784%	$23.815	$23.82	$23.80	$23.80
7 purchase totals =	$792.27		$864.7127	$864.73	$864.80	$864.70