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	$156.69	8.265%	$169.6404	$169.64	$169.65	$169.60
Purchase #2	$94.85	4.555%	$99.1704	$99.17	$99.15	$99.20
Purchase #3	$75.71	10.845%	$83.9207	$83.92	$83.90	$83.90
Purchase #4	$216.78	6.607%	$231.1027	$231.10	$231.10	$231.10
Purchase #5	$156.29	6.293%	$166.1253	$166.13	$166.15	$166.10
Purchase #6	$83.91	9.111%	$91.555	$91.56	$91.55	$91.60
Purchase #7	$83.55	9.366%	$91.3753	$91.38	$91.40	$91.40
7 purchase totals =	$867.78		$932.8898	$932.90	$932.90	$932.90