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	$62.99	6.429%	$67.0396	$67.04	$67.05	$67.00
Purchase #2	$160.72	4.735%	$168.3301	$168.33	$168.35	$168.30
Purchase #3	$8.59	3.764%	$8.9133	$8.91	$8.90	$8.90
Purchase #4	$45.67	7.669%	$49.1724	$49.17	$49.15	$49.20
Purchase #5	$74.46	10.851%	$82.5397	$82.54	$82.55	$82.50
Purchase #6	$114.82	13.351%	$130.1496	$130.15	$130.15	$130.10
Purchase #7	$227.52	8.681%	$247.271	$247.27	$247.25	$247.30
7 purchase totals =	$694.77		$753.4157	$753.41	$753.40	$753.30