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	$91.39	11.421%	$101.8277	$101.83	$101.85	$101.80
Purchase #2	$134.37	3.525%	$139.1065	$139.11	$139.10	$139.10
Purchase #3	$92.25	7.865%	$99.5055	$99.51	$99.50	$99.50
Purchase #4	$137.60	10.183%	$151.6118	$151.61	$151.60	$151.60
Purchase #5	$69.44	10.206%	$76.527	$76.53	$76.55	$76.50
Purchase #6	$250.47	3.221%	$258.5376	$258.54	$258.55	$258.50
Purchase #7	$235.74	6.129%	$250.1885	$250.19	$250.20	$250.20
7 purchase totals =	$1,011.26		$1,077.3046	$1,077.32	$1,077.35	$1,077.20