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	$190.89	5.382%	$201.1637	$201.16	$201.15	$201.20
Purchase #2	$103.31	12.171%	$115.8839	$115.88	$115.90	$115.90
Purchase #3	$94.47	5.502%	$99.6677	$99.67	$99.65	$99.70
Purchase #4	$69.70	12.503%	$78.4146	$78.41	$78.40	$78.40
Purchase #5	$124.92	12.178%	$140.1328	$140.13	$140.15	$140.10
Purchase #6	$159.95	3.328%	$165.2731	$165.27	$165.25	$165.30
Purchase #7	$161.65	4.714%	$169.2702	$169.27	$169.25	$169.30
7 purchase totals =	$904.89		$969.8060	$969.79	$969.75	$969.90