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	$80.25	13.670%	$91.2202	$91.22	$91.20	$91.20
Purchase #2	$64.48	13.663%	$73.2899	$73.29	$73.30	$73.30
Purchase #3	$226.79	12.359%	$254.819	$254.82	$254.80	$254.80
Purchase #4	$79.84	12.212%	$89.5901	$89.59	$89.60	$89.60
Purchase #5	$92.39	10.604%	$102.187	$102.19	$102.20	$102.20
Purchase #6	$128.41	8.658%	$139.5277	$139.53	$139.55	$139.50
Purchase #7	$7.32	5.459%	$7.7196	$7.72	$7.70	$7.70
7 purchase totals =	$679.48		$758.3535	$758.36	$758.35	$758.30