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	$207.33	6.856%	$221.5445	$221.54	$221.55	$221.50
Purchase #2	$61.95	5.390%	$65.2891	$65.29	$65.30	$65.30
Purchase #3	$56.39	10.626%	$62.382	$62.38	$62.40	$62.40
Purchase #4	$185.95	3.676%	$192.7855	$192.79	$192.80	$192.80
Purchase #5	$94.66	5.355%	$99.729	$99.73	$99.75	$99.70
Purchase #6	$42.87	5.405%	$45.1871	$45.19	$45.20	$45.20
Purchase #7	$219.85	11.108%	$244.2709	$244.27	$244.25	$244.30
7 purchase totals =	$869.00		$931.1881	$931.19	$931.25	$931.20