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	$99.73	4.859%	$104.5759	$104.58	$104.60	$104.60
Purchase #2	$143.76	7.396%	$154.3925	$154.39	$154.40	$154.40
Purchase #3	$89.25	6.337%	$94.9058	$94.91	$94.90	$94.90
Purchase #4	$174.40	3.350%	$180.2424	$180.24	$180.25	$180.20
Purchase #5	$70.66	11.752%	$78.964	$78.96	$78.95	$79.00
Purchase #6	$32.32	10.852%	$35.8274	$35.83	$35.85	$35.80
Purchase #7	$90.96	12.549%	$102.3746	$102.37	$102.35	$102.40
7 purchase totals =	$701.08		$751.2826	$751.28	$751.30	$751.30