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	$195.43	5.149%	$205.4927	$205.49	$205.50	$205.50
Purchase #2	$134.74	12.398%	$151.4451	$151.45	$151.45	$151.40
Purchase #3	$180.61	13.173%	$204.4018	$204.40	$204.40	$204.40
Purchase #4	$96.60	7.264%	$103.617	$103.62	$103.60	$103.60
Purchase #5	$136.86	11.317%	$152.3484	$152.35	$152.35	$152.30
Purchase #6	$227.34	7.447%	$244.27	$244.27	$244.25	$244.30
Purchase #7	$61.69	11.155%	$68.5715	$68.57	$68.55	$68.60
7 purchase totals =	$1,033.27		$1,130.1465	$1,130.15	$1,130.10	$1,130.10