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	$113.73	12.550%	$128.0031	$128.00	$128.00	$128.00
Purchase #2	$93.30	7.637%	$100.4253	$100.43	$100.45	$100.40
Purchase #3	$156.60	4.794%	$164.1074	$164.11	$164.10	$164.10
Purchase #4	$90.76	9.470%	$99.355	$99.36	$99.35	$99.40
Purchase #5	$169.37	6.365%	$180.1504	$180.15	$180.15	$180.20
Purchase #6	$177.66	5.414%	$187.2785	$187.28	$187.30	$187.30
Purchase #7	$151.70	9.666%	$166.3633	$166.36	$166.35	$166.40
7 purchase totals =	$953.12		$1,025.6830	$1,025.69	$1,025.70	$1,025.80