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	$215.95	12.580%	$243.1165	$243.12	$243.10	$243.10
Purchase #2	$88.98	8.322%	$96.3849	$96.38	$96.40	$96.40
Purchase #3	$67.46	7.843%	$72.7509	$72.75	$72.75	$72.80
Purchase #4	$242.50	10.779%	$268.6391	$268.64	$268.65	$268.60
Purchase #5	$199.29	7.334%	$213.9059	$213.91	$213.90	$213.90
Purchase #6	$85.27	12.369%	$95.817	$95.82	$95.80	$95.80
Purchase #7	$11.62	3.549%	$12.0324	$12.03	$12.05	$12.00
7 purchase totals =	$911.07		$1,002.6467	$1,002.65	$1,002.65	$1,002.60