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	$211.62	8.138%	$228.8416	$228.84	$228.85	$228.80
Purchase #2	$245.71	8.393%	$266.3324	$266.33	$266.35	$266.30
Purchase #3	$225.59	12.865%	$254.6122	$254.61	$254.60	$254.60
Purchase #4	$234.89	4.234%	$244.8352	$244.84	$244.85	$244.80
Purchase #5	$82.59	9.766%	$90.6557	$90.66	$90.65	$90.70
Purchase #6	$76.82	4.300%	$80.1233	$80.12	$80.10	$80.10
Purchase #7	$24.38	6.351%	$25.9284	$25.93	$25.95	$25.90
7 purchase totals =	$1,101.60		$1,191.3288	$1,191.33	$1,191.35	$1,191.20