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	$129.57	5.495%	$136.6899	$136.69	$136.70	$136.70
Purchase #2	$140.50	10.331%	$155.0151	$155.02	$155.00	$155.00
Purchase #3	$248.75	3.719%	$258.001	$258.00	$258.00	$258.00
Purchase #4	$85.25	4.828%	$89.3659	$89.37	$89.35	$89.40
Purchase #5	$154.38	11.737%	$172.4996	$172.50	$172.50	$172.50
Purchase #6	$103.90	13.675%	$118.1083	$118.11	$118.10	$118.10
Purchase #7	$79.86	3.476%	$82.6359	$82.64	$82.65	$82.60
7 purchase totals =	$942.21		$1,012.3157	$1,012.33	$1,012.30	$1,012.30