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	$97.78	11.736%	$109.2555	$109.26	$109.25	$109.30
Purchase #2	$107.86	5.550%	$113.8462	$113.85	$113.85	$113.80
Purchase #3	$210.62	5.560%	$222.3305	$222.33	$222.35	$222.30
Purchase #4	$107.30	5.668%	$113.3818	$113.38	$113.40	$113.40
Purchase #5	$85.26	6.796%	$91.0543	$91.05	$91.05	$91.10
Purchase #6	$166.55	4.391%	$173.8632	$173.86	$173.85	$173.90
Purchase #7	$194.85	7.514%	$209.491	$209.49	$209.50	$209.50
7 purchase totals =	$970.22		$1,033.2225	$1,033.22	$1,033.25	$1,033.30