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	$111.49	5.470%	$117.5885	$117.59	$117.60	$117.60
Purchase #2	$198.48	6.129%	$210.6448	$210.64	$210.65	$210.60
Purchase #3	$232.93	7.609%	$250.6536	$250.65	$250.65	$250.70
Purchase #4	$119.66	4.804%	$125.4085	$125.41	$125.40	$125.40
Purchase #5	$103.45	9.737%	$113.5229	$113.52	$113.50	$113.50
Purchase #6	$67.51	6.384%	$71.8198	$71.82	$71.80	$71.80
Purchase #7	$147.58	10.139%	$162.5431	$162.54	$162.55	$162.50
7 purchase totals =	$981.10		$1,052.1812	$1,052.17	$1,052.15	$1,052.10