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	$78.91	11.570%	$88.0399	$88.04	$88.05	$88.00
Purchase #2	$74.52	5.649%	$78.7296	$78.73	$78.75	$78.70
Purchase #3	$164.67	4.542%	$172.1493	$172.15	$172.15	$172.10
Purchase #4	$49.56	9.722%	$54.3782	$54.38	$54.40	$54.40
Purchase #5	$112.90	13.469%	$128.1065	$128.11	$128.10	$128.10
Purchase #6	$51.29	11.780%	$57.332	$57.33	$57.35	$57.30
Purchase #7	$135.27	7.568%	$145.5072	$145.51	$145.50	$145.50
7 purchase totals =	$667.12		$724.2427	$724.25	$724.30	$724.10