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	$131.61	8.127%	$142.3059	$142.31	$142.30	$142.30
Purchase #2	$98.88	3.809%	$102.6463	$102.65	$102.65	$102.60
Purchase #3	$102.53	6.855%	$109.5584	$109.56	$109.55	$109.60
Purchase #4	$193.88	9.647%	$212.5836	$212.58	$212.60	$212.60
Purchase #5	$223.56	7.291%	$239.8598	$239.86	$239.85	$239.90
Purchase #6	$57.31	6.763%	$61.1859	$61.19	$61.20	$61.20
Purchase #7	$53.42	7.325%	$57.333	$57.33	$57.35	$57.30
7 purchase totals =	$861.19		$925.4729	$925.48	$925.50	$925.50