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	$172.58	11.245%	$191.9866	$191.99	$192.00	$192.00
Purchase #2	$62.45	9.602%	$68.4464	$68.45	$68.45	$68.40
Purchase #3	$104.27	4.793%	$109.2677	$109.27	$109.25	$109.30
Purchase #4	$170.53	6.152%	$181.021	$181.02	$181.00	$181.00
Purchase #5	$228.26	8.821%	$248.3948	$248.39	$248.40	$248.40
Purchase #6	$76.30	12.203%	$85.6109	$85.61	$85.60	$85.60
Purchase #7	$88.72	11.745%	$99.1402	$99.14	$99.15	$99.10
7 purchase totals =	$903.11		$983.8676	$983.87	$983.85	$983.80