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	$91.65	7.452%	$98.4798	$98.48	$98.50	$98.50
Purchase #2	$40.90	7.870%	$44.1188	$44.12	$44.10	$44.10
Purchase #3	$31.31	7.280%	$33.5894	$33.59	$33.60	$33.60
Purchase #4	$242.48	4.654%	$253.765	$253.77	$253.75	$253.80
Purchase #5	$178.88	9.671%	$196.1795	$196.18	$196.20	$196.20
Purchase #6	$29.35	9.502%	$32.1388	$32.14	$32.15	$32.10
Purchase #7	$147.61	12.744%	$166.4214	$166.42	$166.40	$166.40
7 purchase totals =	$762.18		$824.6927	$824.70	$824.70	$824.70