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	$191.76	4.450%	$200.2933	$200.29	$200.30	$200.30
Purchase #2	$81.32	4.397%	$84.8956	$84.90	$84.90	$84.90
Purchase #3	$103.71	8.185%	$112.1987	$112.20	$112.20	$112.20
Purchase #4	$17.69	12.234%	$19.8542	$19.85	$19.85	$19.90
Purchase #5	$243.25	11.795%	$271.9413	$271.94	$271.95	$271.90
Purchase #6	$139.54	9.426%	$152.693	$152.69	$152.70	$152.70
Purchase #7	$216.85	11.780%	$242.3949	$242.39	$242.40	$242.40
7 purchase totals =	$994.12		$1,084.2710	$1,084.26	$1,084.30	$1,084.30