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	$70.91	8.209%	$76.731	$76.73	$76.75	$76.70
Purchase #2	$64.92	12.207%	$72.8448	$72.84	$72.85	$72.80
Purchase #3	$134.25	6.146%	$142.501	$142.50	$142.50	$142.50
Purchase #4	$79.94	3.575%	$82.7979	$82.80	$82.80	$82.80
Purchase #5	$226.78	9.469%	$248.2538	$248.25	$248.25	$248.30
Purchase #6	$189.77	10.499%	$209.694	$209.69	$209.70	$209.70
Purchase #7	$247.46	9.283%	$270.4317	$270.43	$270.45	$270.40
7 purchase totals =	$1,014.03		$1,103.2542	$1,103.24	$1,103.30	$1,103.20