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	$234.82	4.362%	$245.0628	$245.06	$245.05	$245.10
Purchase #2	$242.49	13.443%	$275.0879	$275.09	$275.10	$275.10
Purchase #3	$99.59	8.155%	$107.7116	$107.71	$107.70	$107.70
Purchase #4	$188.45	13.317%	$213.5459	$213.55	$213.55	$213.50
Purchase #5	$64.78	8.838%	$70.5053	$70.51	$70.50	$70.50
Purchase #6	$62.96	13.276%	$71.3186	$71.32	$71.30	$71.30
Purchase #7	$100.80	5.231%	$106.0728	$106.07	$106.05	$106.10
7 purchase totals =	$993.89		$1,089.3049	$1,089.31	$1,089.25	$1,089.30