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	$230.75	5.290%	$242.9567	$242.96	$242.95	$243.00
Purchase #2	$34.52	3.294%	$35.6571	$35.66	$35.65	$35.70
Purchase #3	$210.62	4.242%	$219.5545	$219.55	$219.55	$219.60
Purchase #4	$110.82	11.524%	$123.5909	$123.59	$123.60	$123.60
Purchase #5	$166.43	4.797%	$174.4136	$174.41	$174.40	$174.40
Purchase #6	$57.43	3.554%	$59.4711	$59.47	$59.45	$59.50
Purchase #7	$114.71	5.161%	$120.6302	$120.63	$120.65	$120.60
7 purchase totals =	$925.28		$976.2741	$976.27	$976.25	$976.40