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	$52.53	11.558%	$58.6014	$58.60	$58.60	$58.60
Purchase #2	$229.33	7.236%	$245.9243	$245.92	$245.90	$245.90
Purchase #3	$203.26	6.443%	$216.356	$216.36	$216.35	$216.40
Purchase #4	$56.47	4.453%	$58.9846	$58.98	$59.00	$59.00
Purchase #5	$73.27	12.488%	$82.42	$82.42	$82.40	$82.40
Purchase #6	$71.96	10.440%	$79.4726	$79.47	$79.45	$79.50
Purchase #7	$69.89	11.326%	$77.8057	$77.81	$77.80	$77.80
7 purchase totals =	$756.71		$819.5646	$819.56	$819.50	$819.60