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	$109.84	5.556%	$115.9427	$115.94	$115.95	$115.90
Purchase #2	$249.89	8.489%	$271.1032	$271.10	$271.10	$271.10
Purchase #3	$245.34	11.381%	$273.2621	$273.26	$273.25	$273.30
Purchase #4	$42.97	9.199%	$46.9228	$46.92	$46.90	$46.90
Purchase #5	$104.77	8.168%	$113.3276	$113.33	$113.35	$113.30
Purchase #6	$24.30	11.380%	$27.0653	$27.07	$27.05	$27.10
Purchase #7	$160.35	7.435%	$172.272	$172.27	$172.25	$172.30
7 purchase totals =	$937.46		$1,019.8957	$1,019.89	$1,019.85	$1,019.90