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	$163.54	12.555%	$184.0724	$184.07	$184.05	$184.10
Purchase #2	$128.89	9.103%	$140.6229	$140.62	$140.60	$140.60
Purchase #3	$181.78	7.368%	$195.1736	$195.17	$195.15	$195.20
Purchase #4	$212.72	9.722%	$233.4006	$233.40	$233.40	$233.40
Purchase #5	$90.41	9.645%	$99.13	$99.13	$99.15	$99.10
Purchase #6	$65.42	11.687%	$73.0656	$73.07	$73.05	$73.10
Purchase #7	$124.98	8.703%	$135.857	$135.86	$135.85	$135.90
7 purchase totals =	$967.74		$1,061.3221	$1,061.32	$1,061.25	$1,061.40