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	$193.57	3.776%	$200.8792	$200.88	$200.90	$200.90
Purchase #2	$121.88	4.413%	$127.2586	$127.26	$127.25	$127.30
Purchase #3	$103.57	5.821%	$109.5988	$109.60	$109.60	$109.60
Purchase #4	$240.56	5.644%	$254.1372	$254.14	$254.15	$254.10
Purchase #5	$191.85	12.422%	$215.6816	$215.68	$215.70	$215.70
Purchase #6	$250.65	8.744%	$272.5668	$272.57	$272.55	$272.60
Purchase #7	$205.50	11.812%	$229.7737	$229.77	$229.75	$229.80
7 purchase totals =	$1,307.58		$1,409.8959	$1,409.90	$1,409.90	$1,410.00