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	$182.68	8.523%	$198.2498	$198.25	$198.25	$198.20
Purchase #2	$39.57	7.179%	$42.4107	$42.41	$42.40	$42.40
Purchase #3	$151.36	11.279%	$168.4319	$168.43	$168.45	$168.40
Purchase #4	$91.29	8.555%	$99.0999	$99.10	$99.10	$99.10
Purchase #5	$26.60	3.221%	$27.4568	$27.46	$27.45	$27.50
Purchase #6	$184.71	8.279%	$200.0021	$200.00	$200.00	$200.00
Purchase #7	$250.32	7.840%	$269.9451	$269.95	$269.95	$269.90
7 purchase totals =	$926.53		$1,005.5963	$1,005.60	$1,005.60	$1,005.50