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	$111.26	6.172%	$118.127	$118.13	$118.15	$118.10
Purchase #2	$178.60	5.794%	$188.9481	$188.95	$188.95	$188.90
Purchase #3	$36.29	4.232%	$37.8258	$37.83	$37.85	$37.80
Purchase #4	$79.64	12.747%	$89.7917	$89.79	$89.80	$89.80
Purchase #5	$42.88	7.659%	$46.1642	$46.16	$46.15	$46.20
Purchase #6	$51.87	7.716%	$55.8723	$55.87	$55.85	$55.90
Purchase #7	$245.75	7.633%	$264.5081	$264.51	$264.50	$264.50
7 purchase totals =	$746.29		$801.2372	$801.24	$801.25	$801.20