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	$178.37	4.179%	$185.8241	$185.82	$185.80	$185.80
Purchase #2	$98.68	4.654%	$103.2726	$103.27	$103.25	$103.30
Purchase #3	$134.73	10.223%	$148.5034	$148.50	$148.50	$148.50
Purchase #4	$105.65	13.504%	$119.917	$119.92	$119.90	$119.90
Purchase #5	$18.92	9.145%	$20.6502	$20.65	$20.65	$20.70
Purchase #6	$250.49	4.480%	$261.712	$261.71	$261.70	$261.70
Purchase #7	$236.74	3.592%	$245.2437	$245.24	$245.25	$245.20
7 purchase totals =	$1,023.58		$1,085.1230	$1,085.11	$1,085.05	$1,085.10