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	$201.29	13.830%	$229.1284	$229.13	$229.15	$229.10
Purchase #2	$218.91	10.482%	$241.8561	$241.86	$241.85	$241.90
Purchase #3	$47.48	12.860%	$53.5859	$53.59	$53.60	$53.60
Purchase #4	$99.38	4.144%	$103.4983	$103.50	$103.50	$103.50
Purchase #5	$110.39	7.320%	$118.4705	$118.47	$118.45	$118.50
Purchase #6	$54.45	3.786%	$56.5115	$56.51	$56.50	$56.50
Purchase #7	$239.96	9.847%	$263.5889	$263.59	$263.60	$263.60
7 purchase totals =	$971.86		$1,066.6396	$1,066.65	$1,066.65	$1,066.70