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	$246.33	7.116%	$263.8588	$263.86	$263.85	$263.90
Purchase #2	$52.59	5.687%	$55.5808	$55.58	$55.60	$55.60
Purchase #3	$154.83	3.223%	$159.8202	$159.82	$159.80	$159.80
Purchase #4	$121.38	3.581%	$125.7266	$125.73	$125.75	$125.70
Purchase #5	$162.46	4.365%	$169.5514	$169.55	$169.55	$169.60
Purchase #6	$137.86	13.817%	$156.9081	$156.91	$156.90	$156.90
Purchase #7	$175.86	7.144%	$188.4234	$188.42	$188.40	$188.40
7 purchase totals =	$1,051.31		$1,119.8693	$1,119.87	$1,119.85	$1,119.90