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	$234.29	4.191%	$244.1091	$244.11	$244.10	$244.10
Purchase #2	$35.82	3.636%	$37.1224	$37.12	$37.10	$37.10
Purchase #3	$130.49	3.319%	$134.821	$134.82	$134.80	$134.80
Purchase #4	$127.71	11.848%	$142.8411	$142.84	$142.85	$142.80
Purchase #5	$181.78	6.232%	$193.1085	$193.11	$193.10	$193.10
Purchase #6	$237.35	10.704%	$262.7559	$262.76	$262.75	$262.80
Purchase #7	$93.40	3.221%	$96.4084	$96.41	$96.40	$96.40
7 purchase totals =	$1,040.84		$1,111.1664	$1,111.17	$1,111.10	$1,111.10