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	$158.63	8.415%	$171.9787	$171.98	$172.00	$172.00
Purchase #2	$113.41	12.497%	$127.5828	$127.58	$127.60	$127.60
Purchase #3	$38.39	7.517%	$41.2758	$41.28	$41.30	$41.30
Purchase #4	$133.42	10.351%	$147.2303	$147.23	$147.25	$147.20
Purchase #5	$83.75	6.749%	$89.4023	$89.40	$89.40	$89.40
Purchase #6	$221.85	6.406%	$236.0617	$236.06	$236.05	$236.10
Purchase #7	$93.77	8.103%	$101.3682	$101.37	$101.35	$101.40
7 purchase totals =	$843.22		$914.8998	$914.90	$914.95	$915.00