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	$226.58	10.814%	$251.0824	$251.08	$251.10	$251.10
Purchase #2	$124.74	5.106%	$131.1092	$131.11	$131.10	$131.10
Purchase #3	$139.41	12.192%	$156.4069	$156.41	$156.40	$156.40
Purchase #4	$71.42	9.395%	$78.1299	$78.13	$78.15	$78.10
Purchase #5	$225.83	4.597%	$236.2114	$236.21	$236.20	$236.20
Purchase #6	$93.76	9.727%	$102.88	$102.88	$102.90	$102.90
Purchase #7	$161.52	8.546%	$175.3235	$175.32	$175.30	$175.30
7 purchase totals =	$1,043.26		$1,131.1433	$1,131.14	$1,131.15	$1,131.10