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	$176.74	4.786%	$185.1988	$185.20	$185.20	$185.20
Purchase #2	$182.94	4.648%	$191.4431	$191.44	$191.45	$191.40
Purchase #3	$116.30	12.513%	$130.8526	$130.85	$130.85	$130.90
Purchase #4	$232.56	12.673%	$262.0323	$262.03	$262.05	$262.00
Purchase #5	$150.26	12.165%	$168.5391	$168.54	$168.55	$168.50
Purchase #6	$10.25	10.316%	$11.3074	$11.31	$11.30	$11.30
Purchase #7	$225.86	4.525%	$236.0802	$236.08	$236.10	$236.10
7 purchase totals =	$1,094.91		$1,185.4535	$1,185.45	$1,185.50	$1,185.40