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	$182.67	7.474%	$196.3228	$196.32	$196.30	$196.30
Purchase #2	$38.43	10.592%	$42.5005	$42.50	$42.50	$42.50
Purchase #3	$88.83	3.590%	$92.019	$92.02	$92.00	$92.00
Purchase #4	$128.98	8.181%	$139.5319	$139.53	$139.55	$139.50
Purchase #5	$147.97	8.834%	$161.0417	$161.04	$161.05	$161.00
Purchase #6	$230.83	8.558%	$250.5844	$250.58	$250.60	$250.60
Purchase #7	$190.61	10.580%	$210.7765	$210.78	$210.80	$210.80
7 purchase totals =	$1,008.32		$1,092.7768	$1,092.77	$1,092.80	$1,092.70