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	$204.63	8.166%	$221.3401	$221.34	$221.35	$221.30
Purchase #2	$98.26	6.729%	$104.8719	$104.87	$104.85	$104.90
Purchase #3	$129.42	9.607%	$141.8534	$141.85	$141.85	$141.90
Purchase #4	$196.48	6.445%	$209.1431	$209.14	$209.15	$209.10
Purchase #5	$46.27	12.213%	$51.921	$51.92	$51.90	$51.90
Purchase #6	$96.51	9.551%	$105.7277	$105.73	$105.75	$105.70
Purchase #7	$161.92	12.117%	$181.5398	$181.54	$181.55	$181.50
7 purchase totals =	$933.49		$1,016.3970	$1,016.39	$1,016.40	$1,016.30