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	$49.33	3.854%	$51.2312	$51.23	$51.25	$51.20
Purchase #2	$107.33	4.468%	$112.1255	$112.13	$112.15	$112.10
Purchase #3	$94.27	11.728%	$105.326	$105.33	$105.35	$105.30
Purchase #4	$44.86	4.709%	$46.9725	$46.97	$46.95	$47.00
Purchase #5	$131.46	9.790%	$144.3299	$144.33	$144.35	$144.30
Purchase #6	$61.37	12.616%	$69.1124	$69.11	$69.10	$69.10
Purchase #7	$245.90	4.487%	$256.9335	$256.93	$256.95	$256.90
7 purchase totals =	$734.52		$786.0310	$786.03	$786.10	$785.90