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	$113.40	4.111%	$118.0619	$118.06	$118.05	$118.10
Purchase #2	$157.39	4.822%	$164.9793	$164.98	$165.00	$165.00
Purchase #3	$209.72	10.412%	$231.556	$231.56	$231.55	$231.60
Purchase #4	$231.54	11.870%	$259.0238	$259.02	$259.00	$259.00
Purchase #5	$75.62	12.643%	$85.1806	$85.18	$85.20	$85.20
Purchase #6	$72.64	13.828%	$82.6847	$82.68	$82.70	$82.70
Purchase #7	$28.63	10.615%	$31.6691	$31.67	$31.65	$31.70
7 purchase totals =	$888.94		$973.1554	$973.15	$973.15	$973.30