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	$87.61	13.258%	$99.2253	$99.23	$99.25	$99.20
Purchase #2	$57.59	4.438%	$60.1458	$60.15	$60.15	$60.10
Purchase #3	$215.69	6.532%	$229.7789	$229.78	$229.80	$229.80
Purchase #4	$188.52	8.872%	$205.2455	$205.25	$205.25	$205.20
Purchase #5	$202.87	7.180%	$217.4361	$217.44	$217.45	$217.40
Purchase #6	$100.68	4.590%	$105.3012	$105.30	$105.30	$105.30
Purchase #7	$227.48	10.288%	$250.8831	$250.88	$250.90	$250.90
7 purchase totals =	$1,080.44		$1,168.0159	$1,168.03	$1,168.10	$1,167.90