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	$160.56	4.803%	$168.2717	$168.27	$168.25	$168.30
Purchase #2	$211.51	11.515%	$235.8654	$235.87	$235.85	$235.90
Purchase #3	$21.53	13.417%	$24.4187	$24.42	$24.40	$24.40
Purchase #4	$165.69	6.812%	$176.9768	$176.98	$177.00	$177.00
Purchase #5	$29.30	13.593%	$33.2827	$33.28	$33.30	$33.30
Purchase #6	$18.63	4.688%	$19.5034	$19.50	$19.50	$19.50
Purchase #7	$152.82	9.481%	$167.3089	$167.31	$167.30	$167.30
7 purchase totals =	$760.04		$825.6276	$825.63	$825.60	$825.70