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	$151.35	8.675%	$164.4796	$164.48	$164.50	$164.50
Purchase #2	$176.40	11.591%	$196.8465	$196.85	$196.85	$196.80
Purchase #3	$63.62	5.790%	$67.3036	$67.30	$67.30	$67.30
Purchase #4	$99.95	10.691%	$110.6357	$110.64	$110.65	$110.60
Purchase #5	$74.32	7.663%	$80.0151	$80.02	$80.00	$80.00
Purchase #6	$41.50	9.671%	$45.5135	$45.51	$45.50	$45.50
Purchase #7	$200.99	13.872%	$228.8713	$228.87	$228.85	$228.90
7 purchase totals =	$808.13		$893.6653	$893.67	$893.65	$893.60