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	$110.33	13.108%	$124.7921	$124.79	$124.80	$124.80
Purchase #2	$134.40	7.498%	$144.4773	$144.48	$144.50	$144.50
Purchase #3	$185.39	13.402%	$210.236	$210.24	$210.25	$210.20
Purchase #4	$109.95	5.825%	$116.3546	$116.35	$116.35	$116.40
Purchase #5	$180.31	4.756%	$188.8855	$188.89	$188.90	$188.90
Purchase #6	$127.32	3.768%	$132.1174	$132.12	$132.10	$132.10
Purchase #7	$105.32	9.693%	$115.5287	$115.53	$115.55	$115.50
7 purchase totals =	$953.02		$1,032.3916	$1,032.40	$1,032.45	$1,032.40