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	$41.60	9.263%	$45.4534	$45.45	$45.45	$45.50
Purchase #2	$196.73	5.273%	$207.1036	$207.10	$207.10	$207.10
Purchase #3	$215.61	3.688%	$223.5617	$223.56	$223.55	$223.60
Purchase #4	$196.98	11.864%	$220.3497	$220.35	$220.35	$220.30
Purchase #5	$118.50	11.179%	$131.7471	$131.75	$131.75	$131.70
Purchase #6	$193.29	8.837%	$210.371	$210.37	$210.35	$210.40
Purchase #7	$51.27	3.220%	$52.9209	$52.92	$52.90	$52.90
7 purchase totals =	$1,013.98		$1,091.5074	$1,091.50	$1,091.45	$1,091.50