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	$185.78	11.420%	$206.9961	$207.00	$207.00	$207.00
Purchase #2	$72.25	4.280%	$75.3423	$75.34	$75.35	$75.30
Purchase #3	$85.76	4.673%	$89.7676	$89.77	$89.75	$89.80
Purchase #4	$135.76	7.239%	$145.5877	$145.59	$145.60	$145.60
Purchase #5	$60.91	6.657%	$64.9648	$64.96	$64.95	$65.00
Purchase #6	$86.85	4.154%	$90.4577	$90.46	$90.45	$90.50
Purchase #7	$140.72	11.139%	$156.3948	$156.39	$156.40	$156.40
7 purchase totals =	$768.03		$829.5110	$829.51	$829.50	$829.60