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	$42.69	3.751%	$44.2913	$44.29	$44.30	$44.30
Purchase #2	$177.34	13.269%	$200.8712	$200.87	$200.85	$200.90
Purchase #3	$206.37	5.506%	$217.7327	$217.73	$217.75	$217.70
Purchase #4	$233.93	3.831%	$242.8919	$242.89	$242.90	$242.90
Purchase #5	$115.74	10.227%	$127.5767	$127.58	$127.60	$127.60
Purchase #6	$224.94	9.118%	$245.45	$245.45	$245.45	$245.50
Purchase #7	$104.32	3.489%	$107.9597	$107.96	$107.95	$108.00
7 purchase totals =	$1,105.33		$1,186.7735	$1,186.77	$1,186.80	$1,186.90