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	$73.52	11.616%	$82.0601	$82.06	$82.05	$82.10
Purchase #2	$84.98	6.764%	$90.728	$90.73	$90.75	$90.70
Purchase #3	$238.91	8.730%	$259.7668	$259.77	$259.75	$259.80
Purchase #4	$217.27	9.308%	$237.4935	$237.49	$237.50	$237.50
Purchase #5	$189.43	11.554%	$211.3167	$211.32	$211.30	$211.30
Purchase #6	$137.44	9.758%	$150.8514	$150.85	$150.85	$150.90
Purchase #7	$73.26	4.559%	$76.5999	$76.60	$76.60	$76.60
7 purchase totals =	$1,014.81		$1,108.8164	$1,108.82	$1,108.80	$1,108.90