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	$151.41	11.318%	$168.5466	$168.55	$168.55	$168.50
Purchase #2	$40.72	5.786%	$43.0761	$43.08	$43.10	$43.10
Purchase #3	$193.63	9.175%	$211.3956	$211.40	$211.40	$211.40
Purchase #4	$139.61	5.172%	$146.8306	$146.83	$146.85	$146.80
Purchase #5	$187.91	12.532%	$211.4589	$211.46	$211.45	$211.50
Purchase #6	$178.42	12.283%	$200.3353	$200.34	$200.35	$200.30
Purchase #7	$165.41	9.364%	$180.899	$180.90	$180.90	$180.90
7 purchase totals =	$1,057.11		$1,162.5421	$1,162.56	$1,162.60	$1,162.50