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	$198.42	10.680%	$219.6113	$219.61	$219.60	$219.60
Purchase #2	$170.73	7.372%	$183.3162	$183.32	$183.30	$183.30
Purchase #3	$148.35	11.872%	$165.9621	$165.96	$165.95	$166.00
Purchase #4	$51.80	12.628%	$58.3413	$58.34	$58.35	$58.30
Purchase #5	$172.85	6.687%	$184.4085	$184.41	$184.40	$184.40
Purchase #6	$28.78	13.585%	$32.6898	$32.69	$32.70	$32.70
Purchase #7	$184.54	8.501%	$200.2277	$200.23	$200.25	$200.20
7 purchase totals =	$955.47		$1,044.5569	$1,044.56	$1,044.55	$1,044.50