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	$209.95	4.468%	$219.3306	$219.33	$219.35	$219.30
Purchase #2	$12.69	11.194%	$14.1105	$14.11	$14.10	$14.10
Purchase #3	$45.66	10.650%	$50.5228	$50.52	$50.50	$50.50
Purchase #4	$139.58	13.471%	$158.3828	$158.38	$158.40	$158.40
Purchase #5	$37.72	4.793%	$39.5279	$39.53	$39.55	$39.50
Purchase #6	$159.80	6.170%	$169.6597	$169.66	$169.65	$169.70
Purchase #7	$154.65	11.116%	$171.8409	$171.84	$171.85	$171.80
7 purchase totals =	$760.05		$823.3752	$823.37	$823.40	$823.30