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	$234.64	12.161%	$263.1746	$263.17	$263.15	$263.20
Purchase #2	$122.28	5.722%	$129.2769	$129.28	$129.30	$129.30
Purchase #3	$141.53	6.272%	$150.4068	$150.41	$150.40	$150.40
Purchase #4	$188.32	4.276%	$196.3726	$196.37	$196.35	$196.40
Purchase #5	$24.92	11.475%	$27.7796	$27.78	$27.80	$27.80
Purchase #6	$217.64	8.266%	$235.6301	$235.63	$235.65	$235.60
Purchase #7	$129.88	13.871%	$147.8957	$147.90	$147.90	$147.90
7 purchase totals =	$1,059.21		$1,150.5363	$1,150.54	$1,150.55	$1,150.60