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	$194.46	13.324%	$220.3699	$220.37	$220.35	$220.40
Purchase #2	$53.62	4.271%	$55.9101	$55.91	$55.90	$55.90
Purchase #3	$196.25	7.145%	$210.2721	$210.27	$210.25	$210.30
Purchase #4	$40.77	4.413%	$42.5692	$42.57	$42.55	$42.60
Purchase #5	$93.32	11.251%	$103.8194	$103.82	$103.80	$103.80
Purchase #6	$221.66	7.681%	$238.6857	$238.69	$238.70	$238.70
Purchase #7	$218.81	10.443%	$241.6603	$241.66	$241.65	$241.70
7 purchase totals =	$1,018.89		$1,113.2867	$1,113.29	$1,113.20	$1,113.40