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	$140.38	5.172%	$147.6405	$147.64	$147.65	$147.60
Purchase #2	$75.96	4.612%	$79.4633	$79.46	$79.45	$79.50
Purchase #3	$88.31	13.511%	$100.2416	$100.24	$100.25	$100.20
Purchase #4	$232.93	10.134%	$256.5351	$256.54	$256.55	$256.50
Purchase #5	$189.71	3.693%	$196.716	$196.72	$196.70	$196.70
Purchase #6	$223.78	4.871%	$234.6803	$234.68	$234.70	$234.70
Purchase #7	$5.79	11.774%	$6.4717	$6.47	$6.45	$6.50
7 purchase totals =	$956.86		$1,021.7485	$1,021.75	$1,021.75	$1,021.70