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	$165.79	13.753%	$188.5911	$188.59	$188.60	$188.60
Purchase #2	$95.58	13.372%	$108.361	$108.36	$108.35	$108.40
Purchase #3	$67.89	10.730%	$75.1746	$75.17	$75.15	$75.20
Purchase #4	$76.94	6.712%	$82.1042	$82.10	$82.10	$82.10
Purchase #5	$59.42	13.759%	$67.5956	$67.60	$67.60	$67.60
Purchase #6	$94.31	10.795%	$104.4908	$104.49	$104.50	$104.50
Purchase #7	$94.98	13.275%	$107.5886	$107.59	$107.60	$107.60
7 purchase totals =	$654.91		$733.9059	$733.90	$733.90	$734.00