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	$233.51	8.784%	$254.0215	$254.02	$254.00	$254.00
Purchase #2	$250.40	8.576%	$271.8743	$271.87	$271.85	$271.90
Purchase #3	$85.88	6.727%	$91.6571	$91.66	$91.65	$91.70
Purchase #4	$56.56	13.363%	$64.1181	$64.12	$64.10	$64.10
Purchase #5	$130.90	8.308%	$141.7752	$141.78	$141.80	$141.80
Purchase #6	$38.57	10.432%	$42.5936	$42.59	$42.60	$42.60
Purchase #7	$185.51	5.665%	$196.0191	$196.02	$196.00	$196.00
7 purchase totals =	$981.33		$1,062.0589	$1,062.06	$1,062.00	$1,062.10