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	$33.95	11.731%	$37.9327	$37.93	$37.95	$37.90
Purchase #2	$130.78	9.393%	$143.0642	$143.06	$143.05	$143.10
Purchase #3	$165.33	10.112%	$182.0482	$182.05	$182.05	$182.00
Purchase #4	$155.41	4.170%	$161.8906	$161.89	$161.90	$161.90
Purchase #5	$219.89	9.343%	$240.4343	$240.43	$240.45	$240.40
Purchase #6	$95.41	10.128%	$105.0731	$105.07	$105.05	$105.10
Purchase #7	$125.47	3.526%	$129.8941	$129.89	$129.90	$129.90
7 purchase totals =	$926.24		$1,000.3372	$1,000.32	$1,000.35	$1,000.30