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	$147.49	13.492%	$167.3894	$167.39	$167.40	$167.40
Purchase #2	$98.94	5.361%	$104.2442	$104.24	$104.25	$104.20
Purchase #3	$79.85	12.588%	$89.9015	$89.90	$89.90	$89.90
Purchase #4	$213.43	10.451%	$235.7356	$235.74	$235.75	$235.70
Purchase #5	$112.27	13.596%	$127.5342	$127.53	$127.55	$127.50
Purchase #6	$201.25	9.736%	$220.8437	$220.84	$220.85	$220.80
Purchase #7	$242.59	4.734%	$254.0742	$254.07	$254.05	$254.10
7 purchase totals =	$1,095.82		$1,199.7228	$1,199.71	$1,199.75	$1,199.60