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	$178.49	10.352%	$196.9673	$196.97	$196.95	$197.00
Purchase #2	$42.96	3.368%	$44.4069	$44.41	$44.40	$44.40
Purchase #3	$52.77	9.270%	$57.6618	$57.66	$57.65	$57.70
Purchase #4	$38.50	7.853%	$41.5234	$41.52	$41.50	$41.50
Purchase #5	$88.33	7.822%	$95.2392	$95.24	$95.25	$95.20
Purchase #6	$82.50	3.413%	$85.3157	$85.32	$85.30	$85.30
Purchase #7	$236.56	13.123%	$267.6038	$267.60	$267.60	$267.60
7 purchase totals =	$720.11		$788.7181	$788.72	$788.65	$788.70