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	$13.28	5.239%	$13.9757	$13.98	$14.00	$14.00
Purchase #2	$31.87	3.718%	$33.0549	$33.05	$33.05	$33.10
Purchase #3	$195.42	13.720%	$222.2316	$222.23	$222.25	$222.20
Purchase #4	$188.32	11.546%	$210.0634	$210.06	$210.05	$210.10
Purchase #5	$101.99	10.179%	$112.3716	$112.37	$112.35	$112.40
Purchase #6	$17.74	10.472%	$19.5977	$19.60	$19.60	$19.60
Purchase #7	$108.35	13.809%	$123.3121	$123.31	$123.30	$123.30
7 purchase totals =	$656.97		$734.6070	$734.60	$734.60	$734.70