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	$82.56	12.194%	$92.6274	$92.63	$92.65	$92.60
Purchase #2	$93.91	12.196%	$105.3633	$105.36	$105.35	$105.40
Purchase #3	$70.42	11.358%	$78.4183	$78.42	$78.40	$78.40
Purchase #4	$47.78	5.507%	$50.4112	$50.41	$50.40	$50.40
Purchase #5	$81.84	11.263%	$91.0576	$91.06	$91.05	$91.10
Purchase #6	$12.82	7.264%	$13.7512	$13.75	$13.75	$13.80
Purchase #7	$215.91	11.755%	$241.2902	$241.29	$241.30	$241.30
7 purchase totals =	$605.24		$672.9192	$672.92	$672.90	$673.00