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	$142.75	4.450%	$149.1024	$149.10	$149.10	$149.10
Purchase #2	$75.46	6.573%	$80.42	$80.42	$80.40	$80.40
Purchase #3	$103.63	7.321%	$111.2168	$111.22	$111.20	$111.20
Purchase #4	$226.61	8.520%	$245.9172	$245.92	$245.90	$245.90
Purchase #5	$107.62	6.356%	$114.4603	$114.46	$114.45	$114.50
Purchase #6	$7.82	10.822%	$8.6663	$8.67	$8.65	$8.70
Purchase #7	$157.76	5.156%	$165.8941	$165.89	$165.90	$165.90
7 purchase totals =	$821.65		$875.6771	$875.68	$875.60	$875.70