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	$41.98	12.607%	$47.2724	$47.27	$47.25	$47.30
Purchase #2	$55.40	11.705%	$61.8846	$61.88	$61.90	$61.90
Purchase #3	$67.35	6.269%	$71.5722	$71.57	$71.55	$71.60
Purchase #4	$201.72	7.533%	$216.9156	$216.92	$216.90	$216.90
Purchase #5	$49.28	4.306%	$51.402	$51.40	$51.40	$51.40
Purchase #6	$238.49	13.165%	$269.8872	$269.89	$269.90	$269.90
Purchase #7	$98.30	5.180%	$103.3919	$103.39	$103.40	$103.40
7 purchase totals =	$752.52		$822.3259	$822.32	$822.30	$822.40