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	$167.31	12.683%	$188.5299	$188.53	$188.55	$188.50
Purchase #2	$87.79	10.349%	$96.8754	$96.88	$96.90	$96.90
Purchase #3	$41.46	5.469%	$43.7274	$43.73	$43.75	$43.70
Purchase #4	$213.36	12.764%	$240.5933	$240.59	$240.60	$240.60
Purchase #5	$144.92	13.752%	$164.8494	$164.85	$164.85	$164.80
Purchase #6	$85.31	7.300%	$91.5376	$91.54	$91.55	$91.50
Purchase #7	$169.56	10.736%	$187.764	$187.76	$187.75	$187.80
7 purchase totals =	$909.71		$1,013.8770	$1,013.88	$1,013.95	$1,013.80