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	$56.83	13.606%	$64.5623	$64.56	$64.55	$64.60
Purchase #2	$99.76	10.308%	$110.0433	$110.04	$110.05	$110.00
Purchase #3	$196.51	9.428%	$215.037	$215.04	$215.05	$215.00
Purchase #4	$73.91	5.864%	$78.2441	$78.24	$78.25	$78.20
Purchase #5	$234.96	10.225%	$258.9847	$258.98	$259.00	$259.00
Purchase #6	$149.57	4.289%	$155.9851	$155.99	$156.00	$156.00
Purchase #7	$162.73	6.166%	$172.7639	$172.76	$172.75	$172.80
7 purchase totals =	$974.27		$1,055.6204	$1,055.61	$1,055.65	$1,055.60