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	$174.71	8.298%	$189.2074	$189.21	$189.20	$189.20
Purchase #2	$168.83	6.611%	$179.9914	$179.99	$180.00	$180.00
Purchase #3	$210.65	4.330%	$219.7711	$219.77	$219.75	$219.80
Purchase #4	$65.76	10.456%	$72.6359	$72.64	$72.65	$72.60
Purchase #5	$54.60	6.476%	$58.1359	$58.14	$58.15	$58.10
Purchase #6	$169.54	12.245%	$190.3002	$190.30	$190.30	$190.30
Purchase #7	$157.38	8.821%	$171.2625	$171.26	$171.25	$171.30
7 purchase totals =	$1,001.47		$1,081.3044	$1,081.31	$1,081.30	$1,081.30