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	$200.96	10.624%	$222.31	$222.31	$222.30	$222.30
Purchase #2	$211.97	3.538%	$219.4695	$219.47	$219.45	$219.50
Purchase #3	$9.97	13.588%	$11.3247	$11.32	$11.30	$11.30
Purchase #4	$167.35	8.824%	$182.117	$182.12	$182.10	$182.10
Purchase #5	$170.76	10.444%	$188.5942	$188.59	$188.60	$188.60
Purchase #6	$36.42	8.304%	$39.4443	$39.44	$39.45	$39.40
Purchase #7	$204.37	9.378%	$223.5358	$223.54	$223.55	$223.50
7 purchase totals =	$1,001.80		$1,086.7955	$1,086.79	$1,086.75	$1,086.70