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	$220.75	3.568%	$228.6264	$228.63	$228.65	$228.60
Purchase #2	$14.47	5.612%	$15.2821	$15.28	$15.30	$15.30
Purchase #3	$61.74	8.649%	$67.0799	$67.08	$67.10	$67.10
Purchase #4	$89.95	11.467%	$100.2646	$100.26	$100.25	$100.30
Purchase #5	$92.41	4.562%	$96.6257	$96.63	$96.65	$96.60
Purchase #6	$68.46	4.600%	$71.6092	$71.61	$71.60	$71.60
Purchase #7	$45.73	7.758%	$49.2777	$49.28	$49.30	$49.30
7 purchase totals =	$593.51		$628.7656	$628.77	$628.85	$628.80