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	$131.60	10.400%	$145.2864	$145.29	$145.30	$145.30
Purchase #2	$96.61	13.190%	$109.3529	$109.35	$109.35	$109.40
Purchase #3	$11.39	10.316%	$12.565	$12.57	$12.55	$12.60
Purchase #4	$81.45	11.274%	$90.6327	$90.63	$90.65	$90.60
Purchase #5	$246.98	6.501%	$263.0362	$263.04	$263.05	$263.00
Purchase #6	$61.34	10.433%	$67.7396	$67.74	$67.75	$67.70
Purchase #7	$168.32	11.750%	$188.0976	$188.10	$188.10	$188.10
7 purchase totals =	$797.69		$876.7104	$876.72	$876.75	$876.70