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	$91.27	11.577%	$101.8363	$101.84	$101.85	$101.80
Purchase #2	$37.81	5.566%	$39.9145	$39.91	$39.90	$39.90
Purchase #3	$43.61	4.233%	$45.456	$45.46	$45.45	$45.50
Purchase #4	$178.28	10.467%	$196.9406	$196.94	$196.95	$196.90
Purchase #5	$5.74	6.692%	$6.1241	$6.12	$6.10	$6.10
Purchase #6	$17.76	10.111%	$19.5557	$19.56	$19.55	$19.60
Purchase #7	$130.36	9.765%	$143.0897	$143.09	$143.10	$143.10
7 purchase totals =	$504.83		$552.9169	$552.92	$552.90	$552.90