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	$155.47	10.233%	$171.3792	$171.38	$171.40	$171.40
Purchase #2	$190.34	5.372%	$200.5651	$200.57	$200.55	$200.60
Purchase #3	$85.62	12.402%	$96.2386	$96.24	$96.25	$96.20
Purchase #4	$79.55	12.828%	$89.7547	$89.75	$89.75	$89.80
Purchase #5	$57.42	12.155%	$64.3994	$64.40	$64.40	$64.40
Purchase #6	$144.45	11.121%	$160.5143	$160.51	$160.50	$160.50
Purchase #7	$205.66	6.365%	$218.7503	$218.75	$218.75	$218.80
7 purchase totals =	$918.51		$1,001.6016	$1,001.60	$1,001.60	$1,001.70