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	$184.76	5.347%	$194.6391	$194.64	$194.65	$194.60
Purchase #2	$109.89	3.206%	$113.4131	$113.41	$113.40	$113.40
Purchase #3	$224.39	12.330%	$252.0573	$252.06	$252.05	$252.10
Purchase #4	$148.95	11.254%	$165.7128	$165.71	$165.70	$165.70
Purchase #5	$30.73	3.813%	$31.9017	$31.90	$31.90	$31.90
Purchase #6	$240.61	6.739%	$256.8247	$256.82	$256.80	$256.80
Purchase #7	$79.50	12.108%	$89.1259	$89.13	$89.15	$89.10
7 purchase totals =	$1,018.83		$1,103.6746	$1,103.67	$1,103.65	$1,103.60