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	$173.27	13.531%	$196.7152	$196.72	$196.70	$196.70
Purchase #2	$124.85	11.410%	$139.0954	$139.10	$139.10	$139.10
Purchase #3	$211.82	6.110%	$224.7622	$224.76	$224.75	$224.80
Purchase #4	$114.77	8.406%	$124.4176	$124.42	$124.40	$124.40
Purchase #5	$176.50	4.133%	$183.7947	$183.79	$183.80	$183.80
Purchase #6	$78.55	9.541%	$86.0445	$86.04	$86.05	$86.00
Purchase #7	$54.46	10.598%	$60.2317	$60.23	$60.25	$60.20
7 purchase totals =	$934.22		$1,015.0613	$1,015.06	$1,015.05	$1,015.00