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	$244.41	7.555%	$262.8752	$262.88	$262.90	$262.90
Purchase #2	$81.64	12.561%	$91.8948	$91.89	$91.90	$91.90
Purchase #3	$47.43	10.158%	$52.2479	$52.25	$52.25	$52.20
Purchase #4	$98.68	7.842%	$106.4185	$106.42	$106.40	$106.40
Purchase #5	$148.47	13.541%	$168.5743	$168.57	$168.55	$168.60
Purchase #6	$104.55	4.344%	$109.0917	$109.09	$109.10	$109.10
Purchase #7	$107.45	3.223%	$110.9131	$110.91	$110.90	$110.90
7 purchase totals =	$832.63		$902.0155	$902.01	$902.00	$902.00