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	$129.31	11.468%	$144.1393	$144.14	$144.15	$144.10
Purchase #2	$167.83	9.686%	$184.086	$184.09	$184.10	$184.10
Purchase #3	$205.27	8.320%	$222.3485	$222.35	$222.35	$222.30
Purchase #4	$174.47	5.111%	$183.3872	$183.39	$183.40	$183.40
Purchase #5	$126.36	8.636%	$137.2724	$137.27	$137.25	$137.30
Purchase #6	$47.26	13.113%	$53.4572	$53.46	$53.45	$53.50
Purchase #7	$88.76	5.339%	$93.4989	$93.50	$93.50	$93.50
7 purchase totals =	$939.26		$1,018.1895	$1,018.20	$1,018.20	$1,018.20