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	$207.71	12.372%	$233.4079	$233.41	$233.40	$233.40
Purchase #2	$90.50	4.602%	$94.6648	$94.66	$94.65	$94.70
Purchase #3	$183.30	8.413%	$198.721	$198.72	$198.70	$198.70
Purchase #4	$79.43	12.328%	$89.2221	$89.22	$89.20	$89.20
Purchase #5	$140.91	11.604%	$157.2612	$157.26	$157.25	$157.30
Purchase #6	$203.76	5.574%	$215.1176	$215.12	$215.10	$215.10
Purchase #7	$90.94	4.474%	$95.0087	$95.01	$95.00	$95.00
7 purchase totals =	$996.55		$1,083.4033	$1,083.40	$1,083.30	$1,083.40