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	$159.45	5.461%	$168.1576	$168.16	$168.15	$168.20
Purchase #2	$114.34	5.662%	$120.8139	$120.81	$120.80	$120.80
Purchase #3	$153.85	4.462%	$160.7148	$160.71	$160.70	$160.70
Purchase #4	$85.96	6.467%	$91.519	$91.52	$91.50	$91.50
Purchase #5	$166.48	13.518%	$188.9848	$188.98	$189.00	$189.00
Purchase #6	$205.89	13.851%	$234.4078	$234.41	$234.40	$234.40
Purchase #7	$207.50	3.478%	$214.7169	$214.72	$214.70	$214.70
7 purchase totals =	$1,093.47		$1,179.3148	$1,179.31	$1,179.25	$1,179.30