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	$21.36	3.745%	$22.1599	$22.16	$22.15	$22.20
Purchase #2	$144.69	5.371%	$152.4613	$152.46	$152.45	$152.50
Purchase #3	$50.48	6.746%	$53.8854	$53.89	$53.90	$53.90
Purchase #4	$164.85	8.116%	$178.2292	$178.23	$178.25	$178.20
Purchase #5	$45.28	9.159%	$49.4272	$49.43	$49.45	$49.40
Purchase #6	$160.63	8.218%	$173.8306	$173.83	$173.85	$173.80
Purchase #7	$72.45	6.734%	$77.3288	$77.33	$77.35	$77.30
7 purchase totals =	$659.74		$707.3224	$707.33	$707.40	$707.30