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	$81.92	5.842%	$86.7058	$86.71	$86.70	$86.70
Purchase #2	$213.86	10.557%	$236.4372	$236.44	$236.45	$236.40
Purchase #3	$132.36	11.840%	$148.0314	$148.03	$148.05	$148.00
Purchase #4	$221.63	12.219%	$248.711	$248.71	$248.70	$248.70
Purchase #5	$99.50	5.771%	$105.2421	$105.24	$105.25	$105.20
Purchase #6	$75.50	3.618%	$78.2316	$78.23	$78.25	$78.20
Purchase #7	$100.76	5.159%	$105.9582	$105.96	$105.95	$106.00
7 purchase totals =	$925.53		$1,009.3173	$1,009.32	$1,009.35	$1,009.20