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	$215.88	13.766%	$245.598	$245.60	$245.60	$245.60
Purchase #2	$57.93	3.423%	$59.9129	$59.91	$59.90	$59.90
Purchase #3	$233.92	13.588%	$265.705	$265.71	$265.70	$265.70
Purchase #4	$53.67	6.817%	$57.3287	$57.33	$57.35	$57.30
Purchase #5	$81.48	13.854%	$92.7682	$92.77	$92.75	$92.80
Purchase #6	$191.67	10.732%	$212.24	$212.24	$212.25	$212.20
Purchase #7	$31.31	7.827%	$33.7606	$33.76	$33.75	$33.80
7 purchase totals =	$865.86		$967.3134	$967.32	$967.30	$967.30