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	$133.88	13.360%	$151.7664	$151.77	$151.75	$151.80
Purchase #2	$50.54	3.139%	$52.1265	$52.13	$52.15	$52.10
Purchase #3	$129.29	9.828%	$141.9966	$142.00	$142.00	$142.00
Purchase #4	$196.77	4.641%	$205.9021	$205.90	$205.90	$205.90
Purchase #5	$80.57	12.193%	$90.3939	$90.39	$90.40	$90.40
Purchase #6	$115.32	7.617%	$124.1039	$124.10	$124.10	$124.10
Purchase #7	$79.44	11.741%	$88.7671	$88.77	$88.75	$88.80
7 purchase totals =	$785.81		$855.0565	$855.06	$855.05	$855.10