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	$85.26	12.530%	$95.9431	$95.94	$95.95	$95.90
Purchase #2	$79.82	4.773%	$83.6298	$83.63	$83.65	$83.60
Purchase #3	$88.82	12.118%	$99.5832	$99.58	$99.60	$99.60
Purchase #4	$115.48	3.324%	$119.3186	$119.32	$119.30	$119.30
Purchase #5	$98.33	11.270%	$109.4118	$109.41	$109.40	$109.40
Purchase #6	$22.96	12.558%	$25.8433	$25.84	$25.85	$25.80
Purchase #7	$235.86	11.585%	$263.1844	$263.18	$263.20	$263.20
7 purchase totals =	$726.53		$796.9142	$796.90	$796.95	$796.80