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	$198.69	8.753%	$216.0813	$216.08	$216.10	$216.10
Purchase #2	$55.45	7.740%	$59.7418	$59.74	$59.75	$59.70
Purchase #3	$96.32	7.551%	$103.5931	$103.59	$103.60	$103.60
Purchase #4	$182.45	12.842%	$205.8802	$205.88	$205.90	$205.90
Purchase #5	$73.78	3.761%	$76.5549	$76.55	$76.55	$76.60
Purchase #6	$126.95	4.574%	$132.7567	$132.76	$132.75	$132.80
Purchase #7	$75.47	13.636%	$85.7611	$85.76	$85.75	$85.80
7 purchase totals =	$809.11		$880.3691	$880.36	$880.40	$880.50