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	$98.40	10.125%	$108.363	$108.36	$108.35	$108.40
Purchase #2	$127.72	3.674%	$132.4124	$132.41	$132.40	$132.40
Purchase #3	$238.48	10.139%	$262.6595	$262.66	$262.65	$262.70
Purchase #4	$64.36	12.578%	$72.4552	$72.46	$72.45	$72.50
Purchase #5	$198.46	13.543%	$225.3374	$225.34	$225.35	$225.30
Purchase #6	$240.78	3.690%	$249.6648	$249.66	$249.65	$249.70
Purchase #7	$198.77	12.337%	$223.2923	$223.29	$223.30	$223.30
7 purchase totals =	$1,166.97		$1,274.1846	$1,274.18	$1,274.15	$1,274.30