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	$53.69	5.607%	$56.7004	$56.70	$56.70	$56.70
Purchase #2	$214.43	3.363%	$221.6413	$221.64	$221.65	$221.60
Purchase #3	$201.52	10.790%	$223.264	$223.26	$223.25	$223.30
Purchase #4	$56.42	10.228%	$62.1906	$62.19	$62.20	$62.20
Purchase #5	$102.66	4.109%	$106.8783	$106.88	$106.90	$106.90
Purchase #6	$102.57	6.761%	$109.5048	$109.50	$109.50	$109.50
Purchase #7	$167.60	13.107%	$189.5673	$189.57	$189.55	$189.60
7 purchase totals =	$898.89		$969.7467	$969.74	$969.75	$969.80