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	$102.79	6.381%	$109.349	$109.35	$109.35	$109.30
Purchase #2	$148.27	10.871%	$164.3884	$164.39	$164.40	$164.40
Purchase #3	$40.90	11.513%	$45.6088	$45.61	$45.60	$45.60
Purchase #4	$42.89	9.653%	$47.0302	$47.03	$47.05	$47.00
Purchase #5	$66.55	8.673%	$72.3219	$72.32	$72.30	$72.30
Purchase #6	$114.58	12.164%	$128.5175	$128.52	$128.50	$128.50
Purchase #7	$184.61	11.663%	$206.1411	$206.14	$206.15	$206.10
7 purchase totals =	$700.59		$773.3569	$773.36	$773.35	$773.20