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	$113.85	8.349%	$123.3553	$123.36	$123.35	$123.40
Purchase #2	$17.81	13.731%	$20.2555	$20.26	$20.25	$20.30
Purchase #3	$135.75	6.291%	$144.29	$144.29	$144.30	$144.30
Purchase #4	$200.89	3.275%	$207.4691	$207.47	$207.45	$207.50
Purchase #5	$94.40	4.186%	$98.3516	$98.35	$98.35	$98.40
Purchase #6	$167.47	7.573%	$180.1525	$180.15	$180.15	$180.20
Purchase #7	$50.88	4.132%	$52.9824	$52.98	$53.00	$53.00
7 purchase totals =	$781.05		$826.8564	$826.86	$826.85	$827.10