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	$246.53	5.166%	$259.2657	$259.27	$259.25	$259.30
Purchase #2	$185.28	5.739%	$195.9132	$195.91	$195.90	$195.90
Purchase #3	$161.30	13.148%	$182.5077	$182.51	$182.50	$182.50
Purchase #4	$62.35	12.532%	$70.1637	$70.16	$70.15	$70.20
Purchase #5	$122.88	4.521%	$128.4354	$128.44	$128.45	$128.40
Purchase #6	$41.60	4.534%	$43.4861	$43.49	$43.50	$43.50
Purchase #7	$248.26	10.172%	$273.513	$273.51	$273.50	$273.50
7 purchase totals =	$1,068.20		$1,153.2848	$1,153.29	$1,153.25	$1,153.30