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	$82.29	13.473%	$93.3769	$93.38	$93.40	$93.40
Purchase #2	$115.75	10.427%	$127.8193	$127.82	$127.80	$127.80
Purchase #3	$222.47	7.254%	$238.608	$238.61	$238.60	$238.60
Purchase #4	$151.36	7.544%	$162.7786	$162.78	$162.80	$162.80
Purchase #5	$241.54	3.667%	$250.3973	$250.40	$250.40	$250.40
Purchase #6	$135.48	11.407%	$150.9342	$150.93	$150.95	$150.90
Purchase #7	$71.50	10.558%	$79.049	$79.05	$79.05	$79.00
7 purchase totals =	$1,020.39		$1,102.9633	$1,102.97	$1,103.00	$1,102.90