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	$110.74	11.570%	$123.5526	$123.55	$123.55	$123.60
Purchase #2	$155.27	5.117%	$163.2152	$163.22	$163.20	$163.20
Purchase #3	$12.46	11.475%	$13.8898	$13.89	$13.90	$13.90
Purchase #4	$73.44	11.860%	$82.15	$82.15	$82.15	$82.20
Purchase #5	$92.75	12.545%	$104.3855	$104.39	$104.40	$104.40
Purchase #6	$128.42	13.574%	$145.8517	$145.85	$145.85	$145.90
Purchase #7	$38.32	7.627%	$41.2427	$41.24	$41.25	$41.20
7 purchase totals =	$611.40		$674.2875	$674.29	$674.30	$674.40