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	$179.37	4.683%	$187.7699	$187.77	$187.75	$187.80
Purchase #2	$179.27	6.736%	$191.3456	$191.35	$191.35	$191.30
Purchase #3	$222.65	3.233%	$229.8483	$229.85	$229.85	$229.80
Purchase #4	$122.52	5.144%	$128.8224	$128.82	$128.80	$128.80
Purchase #5	$188.96	11.552%	$210.7887	$210.79	$210.80	$210.80
Purchase #6	$26.58	4.270%	$27.715	$27.72	$27.70	$27.70
Purchase #7	$36.63	13.580%	$41.6044	$41.60	$41.60	$41.60
7 purchase totals =	$955.98		$1,017.8943	$1,017.90	$1,017.85	$1,017.80