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	$62.44	8.765%	$67.9129	$67.91	$67.90	$67.90
Purchase #2	$167.96	11.123%	$186.6422	$186.64	$186.65	$186.60
Purchase #3	$111.58	6.423%	$118.7468	$118.75	$118.75	$118.70
Purchase #4	$244.94	8.171%	$264.954	$264.95	$264.95	$265.00
Purchase #5	$125.56	9.820%	$137.89	$137.89	$137.90	$137.90
Purchase #6	$99.77	8.564%	$108.3143	$108.31	$108.30	$108.30
Purchase #7	$51.75	11.209%	$57.5507	$57.55	$57.55	$57.60
7 purchase totals =	$864.00		$942.0109	$942.00	$942.00	$942.00