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	$162.96	13.652%	$185.2073	$185.21	$185.20	$185.20
Purchase #2	$242.69	9.442%	$265.6048	$265.60	$265.60	$265.60
Purchase #3	$148.56	3.559%	$153.8473	$153.85	$153.85	$153.80
Purchase #4	$85.34	7.288%	$91.5596	$91.56	$91.55	$91.60
Purchase #5	$157.96	4.641%	$165.2909	$165.29	$165.30	$165.30
Purchase #6	$144.90	13.355%	$164.2514	$164.25	$164.25	$164.30
Purchase #7	$114.50	13.519%	$129.9793	$129.98	$130.00	$130.00
7 purchase totals =	$1,056.91		$1,155.7406	$1,155.74	$1,155.75	$1,155.80