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	$94.29	6.816%	$100.7168	$100.72	$100.70	$100.70
Purchase #2	$112.80	12.764%	$127.1978	$127.20	$127.20	$127.20
Purchase #3	$73.44	9.423%	$80.3603	$80.36	$80.35	$80.40
Purchase #4	$69.70	8.129%	$75.3659	$75.37	$75.35	$75.40
Purchase #5	$115.68	10.603%	$127.9456	$127.95	$127.95	$127.90
Purchase #6	$147.45	3.494%	$152.6019	$152.60	$152.60	$152.60
Purchase #7	$51.53	5.578%	$54.4043	$54.40	$54.40	$54.40
7 purchase totals =	$664.89		$718.5926	$718.60	$718.55	$718.60