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	$174.62	11.731%	$195.1047	$195.10	$195.10	$195.10
Purchase #2	$178.41	6.285%	$189.6231	$189.62	$189.60	$189.60
Purchase #3	$136.98	10.808%	$151.7848	$151.78	$151.80	$151.80
Purchase #4	$250.31	4.780%	$262.2748	$262.27	$262.25	$262.30
Purchase #5	$45.72	6.699%	$48.7828	$48.78	$48.80	$48.80
Purchase #6	$172.29	3.488%	$178.2995	$178.30	$178.30	$178.30
Purchase #7	$60.35	8.159%	$65.274	$65.27	$65.25	$65.30
7 purchase totals =	$1,018.68		$1,091.1437	$1,091.12	$1,091.10	$1,091.20