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	$42.95	4.780%	$45.003	$45.00	$45.00	$45.00
Purchase #2	$134.65	12.344%	$151.2712	$151.27	$151.25	$151.30
Purchase #3	$209.56	11.842%	$234.3761	$234.38	$234.40	$234.40
Purchase #4	$51.56	9.248%	$56.3283	$56.33	$56.35	$56.30
Purchase #5	$127.87	12.347%	$143.6581	$143.66	$143.65	$143.70
Purchase #6	$227.81	4.338%	$237.6924	$237.69	$237.70	$237.70
Purchase #7	$126.65	8.433%	$137.3304	$137.33	$137.35	$137.30
7 purchase totals =	$921.05		$1,005.6595	$1,005.66	$1,005.70	$1,005.70