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	$72.54	3.242%	$74.8917	$74.89	$74.90	$74.90
Purchase #2	$100.63	10.696%	$111.3934	$111.39	$111.40	$111.40
Purchase #3	$234.31	11.280%	$260.7402	$260.74	$260.75	$260.70
Purchase #4	$205.65	11.757%	$229.8283	$229.83	$229.85	$229.80
Purchase #5	$177.86	4.116%	$185.1807	$185.18	$185.20	$185.20
Purchase #6	$201.87	8.606%	$219.2429	$219.24	$219.25	$219.20
Purchase #7	$220.67	5.658%	$233.1555	$233.16	$233.15	$233.20
7 purchase totals =	$1,213.53		$1,314.4327	$1,314.43	$1,314.50	$1,314.40