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	$241.53	9.115%	$263.5455	$263.55	$263.55	$263.50
Purchase #2	$241.45	3.589%	$250.1156	$250.12	$250.10	$250.10
Purchase #3	$235.46	3.347%	$243.3408	$243.34	$243.35	$243.30
Purchase #4	$244.98	12.261%	$275.017	$275.02	$275.00	$275.00
Purchase #5	$57.63	3.338%	$59.5537	$59.55	$59.55	$59.60
Purchase #6	$211.27	13.135%	$239.0203	$239.02	$239.00	$239.00
Purchase #7	$152.96	12.387%	$171.9072	$171.91	$171.90	$171.90
7 purchase totals =	$1,385.28		$1,502.5001	$1,502.51	$1,502.45	$1,502.40