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	$204.26	3.640%	$211.6951	$211.70	$211.70	$211.70
Purchase #2	$65.51	9.678%	$71.8501	$71.85	$71.85	$71.90
Purchase #3	$120.76	13.298%	$136.8187	$136.82	$136.80	$136.80
Purchase #4	$183.87	6.384%	$195.6083	$195.61	$195.60	$195.60
Purchase #5	$73.41	7.134%	$78.6471	$78.65	$78.65	$78.60
Purchase #6	$38.51	12.395%	$43.2833	$43.28	$43.30	$43.30
Purchase #7	$45.35	6.700%	$48.3885	$48.39	$48.40	$48.40
7 purchase totals =	$731.67		$786.2911	$786.30	$786.30	$786.30