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	$79.40	4.261%	$82.7832	$82.78	$82.80	$82.80
Purchase #2	$215.70	8.401%	$233.821	$233.82	$233.80	$233.80
Purchase #3	$83.58	11.464%	$93.1616	$93.16	$93.15	$93.20
Purchase #4	$101.87	11.662%	$113.7501	$113.75	$113.75	$113.80
Purchase #5	$229.91	11.298%	$255.8852	$255.89	$255.90	$255.90
Purchase #6	$144.70	8.346%	$156.7767	$156.78	$156.80	$156.80
Purchase #7	$91.84	7.343%	$98.5838	$98.58	$98.60	$98.60
7 purchase totals =	$947.00		$1,034.7616	$1,034.76	$1,034.80	$1,034.90