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	$228.46	6.657%	$243.6686	$243.67	$243.65	$243.70
Purchase #2	$86.48	7.458%	$92.9297	$92.93	$92.95	$92.90
Purchase #3	$103.38	5.166%	$108.7206	$108.72	$108.70	$108.70
Purchase #4	$196.65	11.228%	$218.7299	$218.73	$218.75	$218.70
Purchase #5	$142.82	10.148%	$157.3134	$157.31	$157.30	$157.30
Purchase #6	$85.48	6.369%	$90.9242	$90.92	$90.90	$90.90
Purchase #7	$233.43	4.352%	$243.5889	$243.59	$243.60	$243.60
7 purchase totals =	$1,076.70		$1,155.8753	$1,155.87	$1,155.85	$1,155.80