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	$211.78	7.427%	$227.5089	$227.51	$227.50	$227.50
Purchase #2	$96.92	5.696%	$102.4406	$102.44	$102.45	$102.40
Purchase #3	$42.29	7.155%	$45.3158	$45.32	$45.30	$45.30
Purchase #4	$5.61	11.229%	$6.2399	$6.24	$6.25	$6.20
Purchase #5	$185.73	8.122%	$200.815	$200.82	$200.80	$200.80
Purchase #6	$151.74	8.306%	$164.3435	$164.34	$164.35	$164.30
Purchase #7	$135.75	8.715%	$147.5806	$147.58	$147.60	$147.60
7 purchase totals =	$829.82		$894.2443	$894.25	$894.25	$894.10