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	$46.75	3.699%	$48.4793	$48.48	$48.50	$48.50
Purchase #2	$28.97	6.548%	$30.867	$30.87	$30.85	$30.90
Purchase #3	$236.95	11.186%	$263.4552	$263.46	$263.45	$263.50
Purchase #4	$162.72	7.718%	$175.2787	$175.28	$175.30	$175.30
Purchase #5	$116.39	9.443%	$127.3807	$127.38	$127.40	$127.40
Purchase #6	$54.96	4.413%	$57.3854	$57.39	$57.40	$57.40
Purchase #7	$82.66	9.822%	$90.7789	$90.78	$90.80	$90.80
7 purchase totals =	$729.40		$793.6252	$793.64	$793.70	$793.80