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	$247.63	13.587%	$281.2755	$281.28	$281.30	$281.30
Purchase #2	$169.57	4.623%	$177.4092	$177.41	$177.40	$177.40
Purchase #3	$250.58	4.228%	$261.1745	$261.17	$261.15	$261.20
Purchase #4	$151.32	3.566%	$156.7161	$156.72	$156.70	$156.70
Purchase #5	$72.55	7.814%	$78.2191	$78.22	$78.20	$78.20
Purchase #6	$65.91	4.468%	$68.8549	$68.85	$68.85	$68.90
Purchase #7	$140.39	5.765%	$148.4835	$148.48	$148.50	$148.50
7 purchase totals =	$1,097.95		$1,172.1328	$1,172.13	$1,172.10	$1,172.20