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	$230.60	3.272%	$238.1452	$238.15	$238.15	$238.10
Purchase #2	$179.61	8.869%	$195.5396	$195.54	$195.55	$195.50
Purchase #3	$204.70	6.154%	$217.2972	$217.30	$217.30	$217.30
Purchase #4	$171.94	11.345%	$191.4466	$191.45	$191.45	$191.40
Purchase #5	$104.88	6.259%	$111.4444	$111.44	$111.45	$111.40
Purchase #6	$131.70	10.871%	$146.0171	$146.02	$146.00	$146.00
Purchase #7	$250.90	5.309%	$264.2203	$264.22	$264.20	$264.20
7 purchase totals =	$1,274.33		$1,364.1104	$1,364.12	$1,364.10	$1,363.90