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	$57.56	7.295%	$61.759	$61.76	$61.75	$61.80
Purchase #2	$209.79	9.105%	$228.8914	$228.89	$228.90	$228.90
Purchase #3	$232.55	7.708%	$250.475	$250.48	$250.50	$250.50
Purchase #4	$82.49	10.236%	$90.9337	$90.93	$90.95	$90.90
Purchase #5	$101.60	3.157%	$104.8075	$104.81	$104.80	$104.80
Purchase #6	$135.92	4.465%	$141.9888	$141.99	$142.00	$142.00
Purchase #7	$167.63	3.774%	$173.9564	$173.96	$173.95	$174.00
7 purchase totals =	$987.54		$1,052.8118	$1,052.82	$1,052.85	$1,052.90