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	$39.74	7.765%	$42.8258	$42.83	$42.85	$42.80
Purchase #2	$193.40	8.213%	$209.2839	$209.28	$209.30	$209.30
Purchase #3	$167.41	8.300%	$181.305	$181.31	$181.30	$181.30
Purchase #4	$31.47	7.816%	$33.9297	$33.93	$33.95	$33.90
Purchase #5	$96.38	3.354%	$99.6126	$99.61	$99.60	$99.60
Purchase #6	$249.89	4.198%	$260.3804	$260.38	$260.40	$260.40
Purchase #7	$84.92	3.420%	$87.8243	$87.82	$87.80	$87.80
7 purchase totals =	$863.21		$915.1617	$915.16	$915.20	$915.10