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	$197.91	12.140%	$221.9363	$221.94	$221.95	$221.90
Purchase #2	$200.25	6.705%	$213.6768	$213.68	$213.70	$213.70
Purchase #3	$148.46	12.786%	$167.4421	$167.44	$167.45	$167.40
Purchase #4	$27.72	6.799%	$29.6047	$29.60	$29.60	$29.60
Purchase #5	$56.33	11.699%	$62.92	$62.92	$62.90	$62.90
Purchase #6	$250.43	9.435%	$274.0581	$274.06	$274.05	$274.10
Purchase #7	$84.70	7.395%	$90.9636	$90.96	$90.95	$91.00
7 purchase totals =	$965.80		$1,060.6016	$1,060.60	$1,060.60	$1,060.60