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	$88.97	9.630%	$97.5378	$97.54	$97.55	$97.50
Purchase #2	$47.95	11.571%	$53.4983	$53.50	$53.50	$53.50
Purchase #3	$61.27	5.367%	$64.5584	$64.56	$64.55	$64.60
Purchase #4	$69.67	13.628%	$79.1646	$79.16	$79.15	$79.20
Purchase #5	$65.54	9.215%	$71.5795	$71.58	$71.60	$71.60
Purchase #6	$27.75	4.223%	$28.9219	$28.92	$28.90	$28.90
Purchase #7	$140.61	11.338%	$156.5524	$156.55	$156.55	$156.60
7 purchase totals =	$501.76		$551.8129	$551.81	$551.80	$551.90