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	$55.94	9.368%	$61.1805	$61.18	$61.20	$61.20
Purchase #2	$89.71	7.108%	$96.0866	$96.09	$96.10	$96.10
Purchase #3	$120.41	6.540%	$128.2848	$128.28	$128.30	$128.30
Purchase #4	$234.66	13.430%	$266.1748	$266.17	$266.15	$266.20
Purchase #5	$118.77	10.370%	$131.0864	$131.09	$131.10	$131.10
Purchase #6	$136.30	5.480%	$143.7692	$143.77	$143.75	$143.80
Purchase #7	$102.90	3.175%	$106.1671	$106.17	$106.15	$106.20
7 purchase totals =	$858.69		$932.7494	$932.75	$932.75	$932.90