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	$188.59	4.290%	$196.6805	$196.68	$196.70	$196.70
Purchase #2	$242.30	5.852%	$256.4794	$256.48	$256.50	$256.50
Purchase #3	$214.98	12.591%	$242.0481	$242.05	$242.05	$242.00
Purchase #4	$88.32	9.724%	$96.9082	$96.91	$96.90	$96.90
Purchase #5	$206.99	6.799%	$221.0633	$221.06	$221.05	$221.10
Purchase #6	$64.76	13.360%	$73.4119	$73.41	$73.40	$73.40
Purchase #7	$52.89	7.552%	$56.8843	$56.88	$56.90	$56.90
7 purchase totals =	$1,058.83		$1,143.4757	$1,143.47	$1,143.50	$1,143.50