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	$167.98	6.651%	$179.1523	$179.15	$179.15	$179.20
Purchase #2	$224.39	10.781%	$248.5815	$248.58	$248.60	$248.60
Purchase #3	$225.67	5.518%	$238.1225	$238.12	$238.10	$238.10
Purchase #4	$48.83	11.166%	$54.2824	$54.28	$54.30	$54.30
Purchase #5	$224.46	6.237%	$238.4596	$238.46	$238.45	$238.50
Purchase #6	$122.42	4.592%	$128.0415	$128.04	$128.05	$128.00
Purchase #7	$5.25	9.386%	$5.7428	$5.74	$5.75	$5.70
7 purchase totals =	$1,019.00		$1,092.3826	$1,092.37	$1,092.40	$1,092.40