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	$208.37	5.761%	$220.3742	$220.37	$220.35	$220.40
Purchase #2	$26.25	7.281%	$28.1613	$28.16	$28.15	$28.20
Purchase #3	$54.58	9.522%	$59.7771	$59.78	$59.80	$59.80
Purchase #4	$17.74	6.438%	$18.8821	$18.88	$18.90	$18.90
Purchase #5	$70.31	12.723%	$79.2555	$79.26	$79.25	$79.30
Purchase #6	$175.28	6.826%	$187.2446	$187.24	$187.25	$187.20
Purchase #7	$90.95	11.203%	$101.1391	$101.14	$101.15	$101.10
7 purchase totals =	$643.48		$694.8339	$694.83	$694.85	$694.90