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	$223.43	9.113%	$243.7912	$243.79	$243.80	$243.80
Purchase #2	$244.43	10.391%	$269.8287	$269.83	$269.85	$269.80
Purchase #3	$185.73	5.387%	$195.7353	$195.74	$195.75	$195.70
Purchase #4	$167.79	3.831%	$174.218	$174.22	$174.20	$174.20
Purchase #5	$80.92	10.429%	$89.3591	$89.36	$89.35	$89.40
Purchase #6	$175.96	5.171%	$185.0589	$185.06	$185.05	$185.10
Purchase #7	$51.38	10.590%	$56.8211	$56.82	$56.80	$56.80
7 purchase totals =	$1,129.64		$1,214.8123	$1,214.82	$1,214.80	$1,214.80