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	$156.45	9.597%	$171.4645	$171.46	$171.45	$171.50
Purchase #2	$31.63	6.384%	$33.6493	$33.65	$33.65	$33.60
Purchase #3	$190.68	8.339%	$206.5808	$206.58	$206.60	$206.60
Purchase #4	$42.77	6.117%	$45.3862	$45.39	$45.40	$45.40
Purchase #5	$154.74	12.597%	$174.2326	$174.23	$174.25	$174.20
Purchase #6	$141.71	7.284%	$152.0322	$152.03	$152.05	$152.00
Purchase #7	$234.29	4.596%	$245.058	$245.06	$245.05	$245.10
7 purchase totals =	$952.27		$1,028.4036	$1,028.40	$1,028.45	$1,028.40