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	$92.52	9.425%	$101.24	$101.24	$101.25	$101.20
Purchase #2	$147.56	11.766%	$164.9219	$164.92	$164.90	$164.90
Purchase #3	$152.35	8.240%	$164.9036	$164.90	$164.90	$164.90
Purchase #4	$151.26	11.639%	$168.8652	$168.87	$168.85	$168.90
Purchase #5	$16.77	10.213%	$18.4827	$18.48	$18.50	$18.50
Purchase #6	$89.41	8.411%	$96.9303	$96.93	$96.95	$96.90
Purchase #7	$42.41	10.258%	$46.7604	$46.76	$46.75	$46.80
7 purchase totals =	$692.28		$762.1041	$762.10	$762.10	$762.10