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	$68.33	13.743%	$77.7206	$77.72	$77.70	$77.70
Purchase #2	$205.56	5.250%	$216.3519	$216.35	$216.35	$216.40
Purchase #3	$178.50	11.191%	$198.4759	$198.48	$198.50	$198.50
Purchase #4	$92.59	6.812%	$98.8972	$98.90	$98.90	$98.90
Purchase #5	$168.89	13.314%	$191.376	$191.38	$191.40	$191.40
Purchase #6	$149.70	13.692%	$170.1969	$170.20	$170.20	$170.20
Purchase #7	$194.29	10.443%	$214.5797	$214.58	$214.60	$214.60
7 purchase totals =	$1,057.86		$1,167.5982	$1,167.61	$1,167.65	$1,167.70