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	$137.88	10.302%	$152.0844	$152.08	$152.10	$152.10
Purchase #2	$110.94	11.164%	$123.3253	$123.33	$123.35	$123.30
Purchase #3	$119.92	6.367%	$127.5553	$127.56	$127.55	$127.60
Purchase #4	$129.30	9.142%	$141.1206	$141.12	$141.10	$141.10
Purchase #5	$136.32	11.495%	$151.99	$151.99	$152.00	$152.00
Purchase #6	$188.68	7.269%	$202.3951	$202.40	$202.40	$202.40
Purchase #7	$56.78	5.623%	$59.9727	$59.97	$59.95	$60.00
7 purchase totals =	$879.82		$958.4434	$958.45	$958.45	$958.50