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	$21.76	4.315%	$22.6989	$22.70	$22.70	$22.70
Purchase #2	$236.27	8.681%	$256.7806	$256.78	$256.80	$256.80
Purchase #3	$176.30	12.848%	$198.951	$198.95	$198.95	$199.00
Purchase #4	$71.33	9.687%	$78.2397	$78.24	$78.25	$78.20
Purchase #5	$69.88	3.201%	$72.1169	$72.12	$72.10	$72.10
Purchase #6	$123.70	12.566%	$139.2441	$139.24	$139.25	$139.20
Purchase #7	$168.45	3.837%	$174.9134	$174.91	$174.90	$174.90
7 purchase totals =	$867.69		$942.9446	$942.94	$942.95	$942.90