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	$186.87	3.362%	$193.1526	$193.15	$193.15	$193.20
Purchase #2	$112.87	4.140%	$117.5428	$117.54	$117.55	$117.50
Purchase #3	$91.92	13.668%	$104.4836	$104.48	$104.50	$104.50
Purchase #4	$84.69	6.583%	$90.2651	$90.27	$90.25	$90.30
Purchase #5	$167.57	7.790%	$180.6237	$180.62	$180.60	$180.60
Purchase #6	$142.74	7.477%	$153.4127	$153.41	$153.40	$153.40
Purchase #7	$205.56	7.440%	$220.8537	$220.85	$220.85	$220.90
7 purchase totals =	$992.22		$1,060.3342	$1,060.32	$1,060.30	$1,060.40