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	$184.52	4.660%	$193.1186	$193.12	$193.10	$193.10
Purchase #2	$55.71	6.207%	$59.1679	$59.17	$59.15	$59.20
Purchase #3	$139.61	9.222%	$152.4848	$152.48	$152.50	$152.50
Purchase #4	$53.29	5.309%	$56.1192	$56.12	$56.10	$56.10
Purchase #5	$46.97	11.418%	$52.333	$52.33	$52.35	$52.30
Purchase #6	$56.65	7.299%	$60.7849	$60.78	$60.80	$60.80
Purchase #7	$148.45	11.275%	$165.1877	$165.19	$165.20	$165.20
7 purchase totals =	$685.20		$739.1961	$739.19	$739.20	$739.20