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	$141.76	3.851%	$147.2192	$147.22	$147.20	$147.20
Purchase #2	$110.44	11.358%	$122.9838	$122.98	$123.00	$123.00
Purchase #3	$53.56	3.306%	$55.3307	$55.33	$55.35	$55.30
Purchase #4	$148.91	13.126%	$168.4559	$168.46	$168.45	$168.50
Purchase #5	$104.57	4.695%	$109.4796	$109.48	$109.50	$109.50
Purchase #6	$197.39	12.540%	$222.1427	$222.14	$222.15	$222.10
Purchase #7	$71.33	7.107%	$76.3994	$76.40	$76.40	$76.40
7 purchase totals =	$827.96		$902.0113	$902.01	$902.05	$902.00