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	$238.91	4.421%	$249.4722	$249.47	$249.45	$249.50
Purchase #2	$35.33	4.372%	$36.8746	$36.87	$36.85	$36.90
Purchase #3	$144.74	13.458%	$164.2191	$164.22	$164.20	$164.20
Purchase #4	$47.57	11.185%	$52.8907	$52.89	$52.90	$52.90
Purchase #5	$216.97	9.443%	$237.4585	$237.46	$237.45	$237.50
Purchase #6	$57.64	3.388%	$59.5928	$59.59	$59.60	$59.60
Purchase #7	$195.26	3.793%	$202.6662	$202.67	$202.65	$202.70
7 purchase totals =	$936.42		$1,003.1741	$1,003.17	$1,003.10	$1,003.30