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	$135.59	13.386%	$153.7401	$153.74	$153.75	$153.70
Purchase #2	$102.33	6.798%	$109.2864	$109.29	$109.30	$109.30
Purchase #3	$225.68	3.695%	$234.0189	$234.02	$234.00	$234.00
Purchase #4	$224.29	9.631%	$245.8914	$245.89	$245.90	$245.90
Purchase #5	$61.53	10.718%	$68.1248	$68.12	$68.10	$68.10
Purchase #6	$156.87	11.215%	$174.463	$174.46	$174.45	$174.50
Purchase #7	$113.45	9.166%	$123.8488	$123.85	$123.85	$123.80
7 purchase totals =	$1,019.74		$1,109.3734	$1,109.37	$1,109.35	$1,109.30