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	$228.34	12.504%	$256.8916	$256.89	$256.90	$256.90
Purchase #2	$168.92	3.251%	$174.4116	$174.41	$174.40	$174.40
Purchase #3	$13.68	4.323%	$14.2714	$14.27	$14.25	$14.30
Purchase #4	$39.87	13.575%	$45.2824	$45.28	$45.30	$45.30
Purchase #5	$231.97	13.383%	$263.0145	$263.01	$263.00	$263.00
Purchase #6	$139.26	12.205%	$156.2567	$156.26	$156.25	$156.30
Purchase #7	$218.74	8.513%	$237.3613	$237.36	$237.35	$237.40
7 purchase totals =	$1,040.78		$1,147.4895	$1,147.48	$1,147.45	$1,147.60