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	$118.30	4.482%	$123.6022	$123.60	$123.60	$123.60
Purchase #2	$175.61	3.129%	$181.1048	$181.10	$181.10	$181.10
Purchase #3	$33.25	5.643%	$35.1263	$35.13	$35.15	$35.10
Purchase #4	$195.49	12.476%	$219.8793	$219.88	$219.90	$219.90
Purchase #5	$109.86	6.107%	$116.5692	$116.57	$116.55	$116.60
Purchase #6	$109.41	7.235%	$117.3258	$117.33	$117.35	$117.30
Purchase #7	$81.58	9.463%	$89.2999	$89.30	$89.30	$89.30
7 purchase totals =	$823.50		$882.9075	$882.91	$882.95	$882.90