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	$151.92	12.750%	$171.2898	$171.29	$171.30	$171.30
Purchase #2	$76.67	5.800%	$81.1169	$81.12	$81.10	$81.10
Purchase #3	$160.50	4.559%	$167.8172	$167.82	$167.80	$167.80
Purchase #4	$191.50	9.398%	$209.4972	$209.50	$209.50	$209.50
Purchase #5	$18.26	12.472%	$20.5374	$20.54	$20.55	$20.50
Purchase #6	$109.74	4.350%	$114.5137	$114.51	$114.50	$114.50
Purchase #7	$165.34	11.166%	$183.8019	$183.80	$183.80	$183.80
7 purchase totals =	$873.93		$948.5741	$948.58	$948.55	$948.50