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	$55.76	6.361%	$59.3069	$59.31	$59.30	$59.30
Purchase #2	$151.43	3.336%	$156.4817	$156.48	$156.50	$156.50
Purchase #3	$113.60	13.329%	$128.7417	$128.74	$128.75	$128.70
Purchase #4	$152.54	6.405%	$162.3102	$162.31	$162.30	$162.30
Purchase #5	$193.32	13.773%	$219.946	$219.95	$219.95	$219.90
Purchase #6	$87.36	6.450%	$92.9947	$92.99	$93.00	$93.00
Purchase #7	$219.57	13.464%	$249.1329	$249.13	$249.15	$249.10
7 purchase totals =	$973.58		$1,068.9141	$1,068.91	$1,068.95	$1,068.80