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	$35.58	7.738%	$38.3332	$38.33	$38.35	$38.30
Purchase #2	$191.48	7.397%	$205.6438	$205.64	$205.65	$205.60
Purchase #3	$156.83	5.409%	$165.3129	$165.31	$165.30	$165.30
Purchase #4	$78.91	11.239%	$87.7787	$87.78	$87.80	$87.80
Purchase #5	$125.77	13.289%	$142.4836	$142.48	$142.50	$142.50
Purchase #6	$110.65	11.182%	$123.0229	$123.02	$123.00	$123.00
Purchase #7	$115.43	10.531%	$127.5859	$127.59	$127.60	$127.60
7 purchase totals =	$814.65		$890.1610	$890.15	$890.20	$890.10