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	$210.32	13.191%	$238.0633	$238.06	$238.05	$238.10
Purchase #2	$82.62	7.182%	$88.5538	$88.55	$88.55	$88.60
Purchase #3	$42.50	7.174%	$45.549	$45.55	$45.55	$45.50
Purchase #4	$232.97	5.490%	$245.7601	$245.76	$245.75	$245.80
Purchase #5	$188.78	13.125%	$213.5574	$213.56	$213.55	$213.60
Purchase #6	$51.93	4.423%	$54.2269	$54.23	$54.25	$54.20
Purchase #7	$82.76	9.415%	$90.5519	$90.55	$90.55	$90.60
7 purchase totals =	$891.88		$976.2624	$976.26	$976.25	$976.40