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	$219.56	12.369%	$246.7174	$246.72	$246.70	$246.70
Purchase #2	$152.87	7.448%	$164.2558	$164.26	$164.25	$164.30
Purchase #3	$38.71	11.550%	$43.181	$43.18	$43.20	$43.20
Purchase #4	$96.71	3.164%	$99.7699	$99.77	$99.75	$99.80
Purchase #5	$168.64	12.763%	$190.1635	$190.16	$190.15	$190.20
Purchase #6	$116.92	11.315%	$130.1495	$130.15	$130.15	$130.10
Purchase #7	$240.87	11.384%	$268.2906	$268.29	$268.30	$268.30
7 purchase totals =	$1,034.28		$1,142.5277	$1,142.53	$1,142.50	$1,142.60