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	$45.43	7.322%	$48.7564	$48.76	$48.75	$48.80
Purchase #2	$203.45	7.621%	$218.9549	$218.95	$218.95	$219.00
Purchase #3	$236.93	13.471%	$268.8468	$268.85	$268.85	$268.80
Purchase #4	$234.41	13.257%	$265.4857	$265.49	$265.50	$265.50
Purchase #5	$43.66	3.435%	$45.1597	$45.16	$45.15	$45.20
Purchase #6	$89.89	11.755%	$100.4566	$100.46	$100.45	$100.50
Purchase #7	$143.36	12.814%	$161.7302	$161.73	$161.75	$161.70
7 purchase totals =	$997.13		$1,109.3903	$1,109.40	$1,109.40	$1,109.50