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	$151.76	11.720%	$169.5463	$169.55	$169.55	$169.50
Purchase #2	$98.89	11.327%	$110.0913	$110.09	$110.10	$110.10
Purchase #3	$170.50	11.542%	$190.1791	$190.18	$190.20	$190.20
Purchase #4	$232.57	7.433%	$249.8569	$249.86	$249.85	$249.90
Purchase #5	$61.83	11.412%	$68.886	$68.89	$68.90	$68.90
Purchase #6	$82.54	7.371%	$88.624	$88.62	$88.60	$88.60
Purchase #7	$130.67	7.349%	$140.2729	$140.27	$140.25	$140.30
7 purchase totals =	$928.76		$1,017.4565	$1,017.46	$1,017.45	$1,017.50