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	$201.95	4.422%	$210.8802	$210.88	$210.90	$210.90
Purchase #2	$218.53	9.848%	$240.0508	$240.05	$240.05	$240.10
Purchase #3	$152.76	4.841%	$160.1551	$160.16	$160.15	$160.20
Purchase #4	$198.41	11.537%	$221.3006	$221.30	$221.30	$221.30
Purchase #5	$95.70	8.144%	$103.4938	$103.49	$103.50	$103.50
Purchase #6	$220.47	10.370%	$243.3327	$243.33	$243.35	$243.30
Purchase #7	$84.35	7.334%	$90.5362	$90.54	$90.55	$90.50
7 purchase totals =	$1,172.17		$1,269.7494	$1,269.75	$1,269.80	$1,269.80