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	$173.77	9.648%	$190.5353	$190.54	$190.55	$190.50
Purchase #2	$143.93	7.617%	$154.8931	$154.89	$154.90	$154.90
Purchase #3	$67.79	5.148%	$71.2798	$71.28	$71.30	$71.30
Purchase #4	$211.93	5.143%	$222.8296	$222.83	$222.85	$222.80
Purchase #5	$96.50	12.164%	$108.2383	$108.24	$108.25	$108.20
Purchase #6	$240.91	3.411%	$249.1274	$249.13	$249.15	$249.10
Purchase #7	$70.51	13.347%	$79.921	$79.92	$79.90	$79.90
7 purchase totals =	$1,005.34		$1,076.8245	$1,076.83	$1,076.90	$1,076.70