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	$100.79	11.790%	$112.6731	$112.67	$112.65	$112.70
Purchase #2	$45.64	4.124%	$47.5222	$47.52	$47.50	$47.50
Purchase #3	$81.58	8.532%	$88.5404	$88.54	$88.55	$88.50
Purchase #4	$89.39	12.221%	$100.3144	$100.31	$100.30	$100.30
Purchase #5	$142.35	9.370%	$155.6882	$155.69	$155.70	$155.70
Purchase #6	$154.30	6.375%	$164.1366	$164.14	$164.15	$164.10
Purchase #7	$93.36	8.235%	$101.0482	$101.05	$101.05	$101.00
7 purchase totals =	$707.41		$769.9231	$769.92	$769.90	$769.80