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	$78.33	4.787%	$82.0797	$82.08	$82.10	$82.10
Purchase #2	$234.50	7.276%	$251.5622	$251.56	$251.55	$251.60
Purchase #3	$210.90	12.363%	$236.9736	$236.97	$236.95	$237.00
Purchase #4	$111.84	5.790%	$118.3155	$118.32	$118.30	$118.30
Purchase #5	$52.64	8.855%	$57.3013	$57.30	$57.30	$57.30
Purchase #6	$191.50	4.757%	$200.6097	$200.61	$200.60	$200.60
Purchase #7	$56.53	9.122%	$61.6867	$61.69	$61.70	$61.70
7 purchase totals =	$936.24		$1,008.5287	$1,008.53	$1,008.50	$1,008.60