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	$248.67	13.445%	$282.1037	$282.10	$282.10	$282.10
Purchase #2	$38.94	7.769%	$41.9652	$41.97	$41.95	$42.00
Purchase #3	$167.87	10.613%	$185.686	$185.69	$185.70	$185.70
Purchase #4	$191.43	10.256%	$211.0631	$211.06	$211.05	$211.10
Purchase #5	$37.61	4.618%	$39.3468	$39.35	$39.35	$39.30
Purchase #6	$177.45	12.836%	$200.2275	$200.23	$200.25	$200.20
Purchase #7	$150.33	13.619%	$170.8034	$170.80	$170.80	$170.80
7 purchase totals =	$1,012.30		$1,131.1957	$1,131.20	$1,131.20	$1,131.20