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	$175.60	5.414%	$185.107	$185.11	$185.10	$185.10
Purchase #2	$230.66	10.406%	$254.6625	$254.66	$254.65	$254.70
Purchase #3	$200.67	4.183%	$209.064	$209.06	$209.05	$209.10
Purchase #4	$132.61	9.814%	$145.6243	$145.62	$145.60	$145.60
Purchase #5	$86.28	5.654%	$91.1583	$91.16	$91.15	$91.20
Purchase #6	$161.80	11.269%	$180.0332	$180.03	$180.05	$180.00
Purchase #7	$74.94	5.220%	$78.8519	$78.85	$78.85	$78.90
7 purchase totals =	$1,062.56		$1,144.5012	$1,144.49	$1,144.45	$1,144.60