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	$234.54	3.793%	$243.4361	$243.44	$243.45	$243.40
Purchase #2	$112.28	13.276%	$127.1863	$127.19	$127.20	$127.20
Purchase #3	$224.25	4.692%	$234.7718	$234.77	$234.75	$234.80
Purchase #4	$165.88	8.824%	$180.5173	$180.52	$180.50	$180.50
Purchase #5	$144.96	5.299%	$152.6414	$152.64	$152.65	$152.60
Purchase #6	$86.68	6.706%	$92.4928	$92.49	$92.50	$92.50
Purchase #7	$59.72	4.806%	$62.5901	$62.59	$62.60	$62.60
7 purchase totals =	$1,028.31		$1,093.6358	$1,093.64	$1,093.65	$1,093.60