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	$187.84	4.777%	$196.8131	$196.81	$196.80	$196.80
Purchase #2	$140.81	9.488%	$154.1701	$154.17	$154.15	$154.20
Purchase #3	$160.31	11.572%	$178.8611	$178.86	$178.85	$178.90
Purchase #4	$239.65	3.312%	$247.5872	$247.59	$247.60	$247.60
Purchase #5	$186.69	7.152%	$200.0421	$200.04	$200.05	$200.00
Purchase #6	$250.83	4.802%	$262.8749	$262.87	$262.85	$262.90
Purchase #7	$36.27	3.555%	$37.5594	$37.56	$37.55	$37.60
7 purchase totals =	$1,202.40		$1,277.9079	$1,277.90	$1,277.85	$1,278.00