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	$238.30	6.331%	$253.3868	$253.39	$253.40	$253.40
Purchase #2	$91.54	4.636%	$95.7838	$95.78	$95.80	$95.80
Purchase #3	$235.35	4.426%	$245.7666	$245.77	$245.75	$245.80
Purchase #4	$31.33	5.467%	$33.0428	$33.04	$33.05	$33.00
Purchase #5	$130.99	8.835%	$142.563	$142.56	$142.55	$142.60
Purchase #6	$107.69	3.240%	$111.1792	$111.18	$111.20	$111.20
Purchase #7	$85.55	6.102%	$90.7703	$90.77	$90.75	$90.80
7 purchase totals =	$920.75		$972.4925	$972.49	$972.50	$972.60