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	$167.46	3.864%	$173.9307	$173.93	$173.95	$173.90
Purchase #2	$167.44	3.290%	$172.9488	$172.95	$172.95	$172.90
Purchase #3	$103.31	9.252%	$112.8682	$112.87	$112.85	$112.90
Purchase #4	$108.70	4.260%	$113.3306	$113.33	$113.35	$113.30
Purchase #5	$234.76	12.372%	$263.8045	$263.80	$263.80	$263.80
Purchase #6	$37.77	12.215%	$42.3836	$42.38	$42.40	$42.40
Purchase #7	$193.77	12.815%	$218.6016	$218.60	$218.60	$218.60
7 purchase totals =	$1,013.21		$1,097.8680	$1,097.86	$1,097.90	$1,097.80