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	$189.62	4.791%	$198.7047	$198.70	$198.70	$198.70
Purchase #2	$223.43	4.492%	$233.4665	$233.47	$233.45	$233.50
Purchase #3	$81.61	9.373%	$89.2593	$89.26	$89.25	$89.30
Purchase #4	$33.29	7.768%	$35.876	$35.88	$35.90	$35.90
Purchase #5	$202.64	6.472%	$215.7549	$215.75	$215.75	$215.80
Purchase #6	$250.94	7.531%	$269.8383	$269.84	$269.85	$269.80
Purchase #7	$168.67	12.862%	$190.3643	$190.36	$190.35	$190.40
7 purchase totals =	$1,150.20		$1,233.2640	$1,233.26	$1,233.25	$1,233.40