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	$195.29	7.696%	$210.3195	$210.32	$210.30	$210.30
Purchase #2	$101.32	13.369%	$114.8655	$114.87	$114.85	$114.90
Purchase #3	$245.46	4.230%	$255.843	$255.84	$255.85	$255.80
Purchase #4	$21.30	4.673%	$22.2953	$22.30	$22.30	$22.30
Purchase #5	$63.31	11.344%	$70.4919	$70.49	$70.50	$70.50
Purchase #6	$229.86	10.135%	$253.1563	$253.16	$253.15	$253.20
Purchase #7	$171.91	6.104%	$182.4034	$182.40	$182.40	$182.40
7 purchase totals =	$1,028.45		$1,109.3749	$1,109.38	$1,109.35	$1,109.40