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	$179.62	5.864%	$190.1529	$190.15	$190.15	$190.20
Purchase #2	$49.46	7.667%	$53.2521	$53.25	$53.25	$53.30
Purchase #3	$93.83	4.577%	$98.1246	$98.12	$98.10	$98.10
Purchase #4	$91.33	8.593%	$99.178	$99.18	$99.20	$99.20
Purchase #5	$73.46	6.773%	$78.4354	$78.44	$78.45	$78.40
Purchase #6	$52.66	7.794%	$56.7643	$56.76	$56.75	$56.80
Purchase #7	$206.25	11.773%	$230.5318	$230.53	$230.55	$230.50
7 purchase totals =	$746.61		$806.4391	$806.43	$806.45	$806.50