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	$178.70	3.646%	$185.2154	$185.22	$185.20	$185.20
Purchase #2	$45.33	12.303%	$50.9069	$50.91	$50.90	$50.90
Purchase #3	$124.60	11.687%	$139.162	$139.16	$139.15	$139.20
Purchase #4	$184.34	12.841%	$208.0111	$208.01	$208.00	$208.00
Purchase #5	$5.82	5.138%	$6.119	$6.12	$6.10	$6.10
Purchase #6	$51.46	3.126%	$53.0686	$53.07	$53.05	$53.10
Purchase #7	$83.30	4.154%	$86.7603	$86.76	$86.75	$86.80
7 purchase totals =	$673.55		$729.2433	$729.25	$729.15	$729.30