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	$235.67	5.496%	$248.6224	$248.62	$248.60	$248.60
Purchase #2	$79.76	11.772%	$89.1493	$89.15	$89.15	$89.10
Purchase #3	$188.74	10.333%	$208.2425	$208.24	$208.25	$208.20
Purchase #4	$150.69	4.562%	$157.5645	$157.56	$157.55	$157.60
Purchase #5	$173.65	3.558%	$179.8285	$179.83	$179.85	$179.80
Purchase #6	$227.96	7.698%	$245.5084	$245.51	$245.50	$245.50
Purchase #7	$168.25	8.247%	$182.1256	$182.13	$182.15	$182.10
7 purchase totals =	$1,224.72		$1,311.0412	$1,311.04	$1,311.05	$1,310.90