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	$125.47	4.654%	$131.3094	$131.31	$131.30	$131.30
Purchase #2	$179.44	5.575%	$189.4438	$189.44	$189.45	$189.40
Purchase #3	$71.60	6.800%	$76.4688	$76.47	$76.45	$76.50
Purchase #4	$135.53	7.198%	$145.2854	$145.29	$145.30	$145.30
Purchase #5	$55.81	6.368%	$59.364	$59.36	$59.35	$59.40
Purchase #6	$171.29	3.668%	$177.5729	$177.57	$177.55	$177.60
Purchase #7	$127.26	3.627%	$131.8757	$131.88	$131.90	$131.90
7 purchase totals =	$866.40		$911.3200	$911.32	$911.30	$911.40