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	$168.48	7.739%	$181.5187	$181.52	$181.50	$181.50
Purchase #2	$165.68	12.491%	$186.3751	$186.38	$186.40	$186.40
Purchase #3	$79.86	11.750%	$89.2436	$89.24	$89.25	$89.20
Purchase #4	$200.40	10.161%	$220.7626	$220.76	$220.75	$220.80
Purchase #5	$192.43	5.656%	$203.3138	$203.31	$203.30	$203.30
Purchase #6	$104.30	7.225%	$111.8357	$111.84	$111.85	$111.80
Purchase #7	$127.55	5.486%	$134.5474	$134.55	$134.55	$134.50
7 purchase totals =	$1,038.70		$1,127.5969	$1,127.60	$1,127.60	$1,127.50