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	$187.83	5.424%	$198.0179	$198.02	$198.00	$198.00
Purchase #2	$31.81	11.624%	$35.5076	$35.51	$35.50	$35.50
Purchase #3	$89.50	9.814%	$98.2835	$98.28	$98.30	$98.30
Purchase #4	$53.66	10.758%	$59.4327	$59.43	$59.45	$59.40
Purchase #5	$171.58	10.445%	$189.5015	$189.50	$189.50	$189.50
Purchase #6	$227.98	6.376%	$242.516	$242.52	$242.50	$242.50
Purchase #7	$185.96	4.822%	$194.927	$194.93	$194.95	$194.90
7 purchase totals =	$948.32		$1,018.1862	$1,018.19	$1,018.20	$1,018.10