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	$196.77	6.489%	$209.5384	$209.54	$209.55	$209.50
Purchase #2	$150.83	13.692%	$171.4816	$171.48	$171.50	$171.50
Purchase #3	$63.46	9.173%	$69.2812	$69.28	$69.30	$69.30
Purchase #4	$41.59	3.495%	$43.0436	$43.04	$43.05	$43.00
Purchase #5	$142.95	8.635%	$155.2937	$155.29	$155.30	$155.30
Purchase #6	$185.32	3.379%	$191.582	$191.58	$191.60	$191.60
Purchase #7	$238.81	6.143%	$253.4801	$253.48	$253.50	$253.50
7 purchase totals =	$1,019.73		$1,093.7006	$1,093.69	$1,093.80	$1,093.70