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	$59.87	5.408%	$63.1078	$63.11	$63.10	$63.10
Purchase #2	$118.48	6.824%	$126.5651	$126.57	$126.55	$126.60
Purchase #3	$90.88	13.630%	$103.2669	$103.27	$103.25	$103.30
Purchase #4	$167.87	10.700%	$185.8321	$185.83	$185.85	$185.80
Purchase #5	$125.45	6.681%	$133.8313	$133.83	$133.85	$133.80
Purchase #6	$224.71	11.351%	$250.2168	$250.22	$250.20	$250.20
Purchase #7	$224.28	9.524%	$245.6404	$245.64	$245.65	$245.60
7 purchase totals =	$1,011.54		$1,108.4604	$1,108.47	$1,108.45	$1,108.40