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	$127.77	9.742%	$140.2174	$140.22	$140.20	$140.20
Purchase #2	$151.98	9.812%	$166.8923	$166.89	$166.90	$166.90
Purchase #3	$92.58	6.404%	$98.5088	$98.51	$98.50	$98.50
Purchase #4	$157.76	6.133%	$167.4354	$167.44	$167.45	$167.40
Purchase #5	$35.76	12.779%	$40.3298	$40.33	$40.35	$40.30
Purchase #6	$128.51	6.142%	$136.4031	$136.40	$136.40	$136.40
Purchase #7	$250.83	5.155%	$263.7603	$263.76	$263.75	$263.80
7 purchase totals =	$945.19		$1,013.5471	$1,013.55	$1,013.55	$1,013.50