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	$22.76	3.488%	$23.5539	$23.55	$23.55	$23.60
Purchase #2	$184.61	11.297%	$205.4654	$205.47	$205.45	$205.50
Purchase #3	$220.85	3.622%	$228.8492	$228.85	$228.85	$228.80
Purchase #4	$187.27	4.746%	$196.1578	$196.16	$196.15	$196.20
Purchase #5	$147.76	11.416%	$164.6283	$164.63	$164.65	$164.60
Purchase #6	$6.43	9.696%	$7.0535	$7.05	$7.05	$7.10
Purchase #7	$180.72	9.810%	$198.4486	$198.45	$198.45	$198.40
7 purchase totals =	$950.40		$1,024.1567	$1,024.16	$1,024.15	$1,024.20