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	$228.96	10.563%	$253.145	$253.15	$253.15	$253.10
Purchase #2	$166.61	5.221%	$175.3087	$175.31	$175.30	$175.30
Purchase #3	$106.99	7.377%	$114.8827	$114.88	$114.90	$114.90
Purchase #4	$234.52	5.313%	$246.98	$246.98	$247.00	$247.00
Purchase #5	$116.26	6.147%	$123.4065	$123.41	$123.40	$123.40
Purchase #6	$10.85	3.285%	$11.2064	$11.21	$11.20	$11.20
Purchase #7	$78.56	4.807%	$82.3364	$82.34	$82.35	$82.30
7 purchase totals =	$942.75		$1,007.2657	$1,007.28	$1,007.30	$1,007.20