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	$100.87	4.359%	$105.2669	$105.27	$105.25	$105.30
Purchase #2	$206.31	5.677%	$218.0222	$218.02	$218.00	$218.00
Purchase #3	$244.27	8.386%	$264.7545	$264.75	$264.75	$264.80
Purchase #4	$107.87	7.722%	$116.1997	$116.20	$116.20	$116.20
Purchase #5	$178.59	11.202%	$198.5957	$198.60	$198.60	$198.60
Purchase #6	$179.38	11.279%	$199.6123	$199.61	$199.60	$199.60
Purchase #7	$83.79	6.346%	$89.1073	$89.11	$89.10	$89.10
7 purchase totals =	$1,101.08		$1,191.5586	$1,191.56	$1,191.50	$1,191.60