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	$182.45	6.594%	$194.4808	$194.48	$194.50	$194.50
Purchase #2	$116.40	10.864%	$129.0457	$129.05	$129.05	$129.00
Purchase #3	$85.59	6.411%	$91.0772	$91.08	$91.10	$91.10
Purchase #4	$227.49	4.308%	$237.2903	$237.29	$237.30	$237.30
Purchase #5	$221.30	13.638%	$251.4809	$251.48	$251.50	$251.50
Purchase #6	$127.73	10.424%	$141.0446	$141.04	$141.05	$141.00
Purchase #7	$62.64	7.425%	$67.291	$67.29	$67.30	$67.30
7 purchase totals =	$1,023.60		$1,111.7105	$1,111.71	$1,111.80	$1,111.70