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	$93.88	9.222%	$102.5376	$102.54	$102.55	$102.50
Purchase #2	$20.43	8.167%	$22.0985	$22.10	$22.10	$22.10
Purchase #3	$109.44	12.747%	$123.3903	$123.39	$123.40	$123.40
Purchase #4	$210.47	5.769%	$222.612	$222.61	$222.60	$222.60
Purchase #5	$59.91	7.121%	$64.1762	$64.18	$64.20	$64.20
Purchase #6	$99.88	3.474%	$103.3498	$103.35	$103.35	$103.30
Purchase #7	$103.75	4.830%	$108.7611	$108.76	$108.75	$108.80
7 purchase totals =	$697.76		$746.9255	$746.93	$746.95	$746.90