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	$148.75	4.425%	$155.3322	$155.33	$155.35	$155.30
Purchase #2	$115.72	4.298%	$120.6936	$120.69	$120.70	$120.70
Purchase #3	$232.73	4.713%	$243.6986	$243.70	$243.70	$243.70
Purchase #4	$240.75	12.104%	$269.8904	$269.89	$269.90	$269.90
Purchase #5	$39.95	5.572%	$42.176	$42.18	$42.20	$42.20
Purchase #6	$238.89	13.347%	$270.7746	$270.77	$270.75	$270.80
Purchase #7	$27.30	5.310%	$28.7496	$28.75	$28.75	$28.70
7 purchase totals =	$1,044.09		$1,131.3150	$1,131.31	$1,131.35	$1,131.30