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	$134.73	3.412%	$139.327	$139.33	$139.35	$139.30
Purchase #2	$241.56	7.517%	$259.7181	$259.72	$259.70	$259.70
Purchase #3	$146.92	3.690%	$152.3413	$152.34	$152.35	$152.30
Purchase #4	$210.35	6.174%	$223.337	$223.34	$223.35	$223.30
Purchase #5	$106.48	4.612%	$111.3909	$111.39	$111.40	$111.40
Purchase #6	$213.33	11.692%	$238.2725	$238.27	$238.25	$238.30
Purchase #7	$21.94	13.223%	$24.8411	$24.84	$24.85	$24.80
7 purchase totals =	$1,075.31		$1,149.2279	$1,149.23	$1,149.25	$1,149.10