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	$197.83	10.280%	$218.1669	$218.17	$218.15	$218.20
Purchase #2	$230.87	8.482%	$250.4524	$250.45	$250.45	$250.50
Purchase #3	$121.27	3.444%	$125.4465	$125.45	$125.45	$125.40
Purchase #4	$86.57	3.376%	$89.4926	$89.49	$89.50	$89.50
Purchase #5	$208.97	6.623%	$222.8101	$222.81	$222.80	$222.80
Purchase #6	$116.71	9.194%	$127.4403	$127.44	$127.45	$127.40
Purchase #7	$165.71	5.673%	$175.1107	$175.11	$175.10	$175.10
7 purchase totals =	$1,127.93		$1,208.9195	$1,208.92	$1,208.90	$1,208.90