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	$176.70	6.751%	$188.629	$188.63	$188.65	$188.60
Purchase #2	$181.56	3.328%	$187.6023	$187.60	$187.60	$187.60
Purchase #3	$183.76	7.106%	$196.818	$196.82	$196.80	$196.80
Purchase #4	$96.42	5.658%	$101.8754	$101.88	$101.90	$101.90
Purchase #5	$145.97	9.134%	$159.3029	$159.30	$159.30	$159.30
Purchase #6	$82.48	8.706%	$89.6607	$89.66	$89.65	$89.70
Purchase #7	$54.59	4.644%	$57.1252	$57.13	$57.15	$57.10
7 purchase totals =	$921.48		$981.0135	$981.02	$981.05	$981.00