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	$57.44	5.102%	$60.3706	$60.37	$60.35	$60.40
Purchase #2	$247.72	7.327%	$265.8704	$265.87	$265.85	$265.90
Purchase #3	$167.59	6.426%	$178.3593	$178.36	$178.35	$178.40
Purchase #4	$139.43	6.380%	$148.3256	$148.33	$148.35	$148.30
Purchase #5	$99.54	4.711%	$104.2293	$104.23	$104.25	$104.20
Purchase #6	$6.55	13.869%	$7.4584	$7.46	$7.45	$7.50
Purchase #7	$222.43	10.174%	$245.06	$245.06	$245.05	$245.10
7 purchase totals =	$940.70		$1,009.6736	$1,009.68	$1,009.65	$1,009.80