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	$73.98	7.237%	$79.3339	$79.33	$79.35	$79.30
Purchase #2	$63.92	5.693%	$67.559	$67.56	$67.55	$67.60
Purchase #3	$161.98	11.629%	$180.8167	$180.82	$180.80	$180.80
Purchase #4	$218.59	6.822%	$233.5022	$233.50	$233.50	$233.50
Purchase #5	$179.63	4.277%	$187.3128	$187.31	$187.30	$187.30
Purchase #6	$173.58	11.522%	$193.5799	$193.58	$193.60	$193.60
Purchase #7	$108.60	9.103%	$118.4859	$118.49	$118.50	$118.50
7 purchase totals =	$980.28		$1,060.5904	$1,060.59	$1,060.60	$1,060.60