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	$205.48	11.165%	$228.4218	$228.42	$228.40	$228.40
Purchase #2	$78.62	13.694%	$89.3862	$89.39	$89.40	$89.40
Purchase #3	$139.30	9.245%	$152.1783	$152.18	$152.20	$152.20
Purchase #4	$94.41	13.112%	$106.789	$106.79	$106.80	$106.80
Purchase #5	$122.90	8.448%	$133.2826	$133.28	$133.30	$133.30
Purchase #6	$155.44	11.508%	$173.328	$173.33	$173.35	$173.30
Purchase #7	$164.25	11.352%	$182.8957	$182.90	$182.90	$182.90
7 purchase totals =	$960.40		$1,066.2816	$1,066.29	$1,066.35	$1,066.30