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	$50.39	5.634%	$53.229	$53.23	$53.25	$53.20
Purchase #2	$188.60	4.148%	$196.4231	$196.42	$196.40	$196.40
Purchase #3	$29.88	5.624%	$31.5605	$31.56	$31.55	$31.60
Purchase #4	$156.91	3.295%	$162.0802	$162.08	$162.10	$162.10
Purchase #5	$155.43	8.753%	$169.0348	$169.03	$169.05	$169.00
Purchase #6	$78.94	8.840%	$85.9183	$85.92	$85.90	$85.90
Purchase #7	$234.61	7.105%	$251.279	$251.28	$251.30	$251.30
7 purchase totals =	$894.76		$949.5249	$949.52	$949.55	$949.50