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	$189.92	3.636%	$196.8255	$196.83	$196.85	$196.80
Purchase #2	$75.87	13.775%	$86.3211	$86.32	$86.30	$86.30
Purchase #3	$211.82	4.420%	$221.1824	$221.18	$221.20	$221.20
Purchase #4	$146.35	6.248%	$155.4939	$155.49	$155.50	$155.50
Purchase #5	$169.35	9.692%	$185.7634	$185.76	$185.75	$185.80
Purchase #6	$39.74	9.299%	$43.4354	$43.44	$43.45	$43.40
Purchase #7	$150.46	11.555%	$167.8457	$167.85	$167.85	$167.80
7 purchase totals =	$983.51		$1,056.8674	$1,056.87	$1,056.90	$1,056.80