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	$72.41	7.179%	$77.6083	$77.61	$77.60	$77.60
Purchase #2	$149.98	7.625%	$161.416	$161.42	$161.40	$161.40
Purchase #3	$112.44	4.864%	$117.9091	$117.91	$117.90	$117.90
Purchase #4	$214.91	11.758%	$240.1791	$240.18	$240.20	$240.20
Purchase #5	$90.82	13.659%	$103.2251	$103.23	$103.25	$103.20
Purchase #6	$231.30	8.241%	$250.3614	$250.36	$250.35	$250.40
Purchase #7	$173.47	13.472%	$196.8399	$196.84	$196.85	$196.80
7 purchase totals =	$1,045.33		$1,147.5389	$1,147.55	$1,147.55	$1,147.50