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	$161.96	11.248%	$180.1773	$180.18	$180.20	$180.20
Purchase #2	$6.49	12.690%	$7.3136	$7.31	$7.30	$7.30
Purchase #3	$115.89	10.787%	$128.3911	$128.39	$128.40	$128.40
Purchase #4	$89.59	10.386%	$98.8948	$98.89	$98.90	$98.90
Purchase #5	$51.59	5.277%	$54.3124	$54.31	$54.30	$54.30
Purchase #6	$103.48	8.592%	$112.371	$112.37	$112.35	$112.40
Purchase #7	$244.99	3.843%	$254.405	$254.41	$254.40	$254.40
7 purchase totals =	$773.99		$835.8652	$835.86	$835.85	$835.90