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	$224.54	11.843%	$251.1323	$251.13	$251.15	$251.10
Purchase #2	$106.51	5.407%	$112.269	$112.27	$112.25	$112.30
Purchase #3	$40.92	12.171%	$45.9004	$45.90	$45.90	$45.90
Purchase #4	$116.28	7.397%	$124.8812	$124.88	$124.90	$124.90
Purchase #5	$23.64	8.122%	$25.56	$25.56	$25.55	$25.60
Purchase #6	$158.77	10.738%	$175.8187	$175.82	$175.80	$175.80
Purchase #7	$124.73	3.346%	$128.9035	$128.90	$128.90	$128.90
7 purchase totals =	$795.39		$864.4651	$864.46	$864.45	$864.50