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	$74.39	12.464%	$83.662	$83.66	$83.65	$83.70
Purchase #2	$69.26	11.715%	$77.3738	$77.37	$77.35	$77.40
Purchase #3	$85.85	6.558%	$91.48	$91.48	$91.50	$91.50
Purchase #4	$80.48	12.499%	$90.5392	$90.54	$90.55	$90.50
Purchase #5	$218.52	4.461%	$228.2682	$228.27	$228.25	$228.30
Purchase #6	$240.58	11.132%	$267.3614	$267.36	$267.35	$267.40
Purchase #7	$52.31	4.408%	$54.6158	$54.62	$54.60	$54.60
7 purchase totals =	$821.39		$893.3004	$893.30	$893.25	$893.40