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	$95.92	3.163%	$98.9539	$98.95	$98.95	$99.00
Purchase #2	$114.73	13.814%	$130.5788	$130.58	$130.60	$130.60
Purchase #3	$61.82	4.223%	$64.4307	$64.43	$64.45	$64.40
Purchase #4	$25.41	10.754%	$28.1426	$28.14	$28.15	$28.10
Purchase #5	$101.55	10.483%	$112.1955	$112.20	$112.20	$112.20
Purchase #6	$195.69	10.419%	$216.0789	$216.08	$216.10	$216.10
Purchase #7	$186.41	5.232%	$196.163	$196.16	$196.15	$196.20
7 purchase totals =	$781.53		$846.5434	$846.54	$846.60	$846.60