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	$147.69	5.354%	$155.5973	$155.60	$155.60	$155.60
Purchase #2	$198.96	7.494%	$213.8701	$213.87	$213.85	$213.90
Purchase #3	$229.92	10.493%	$254.0455	$254.05	$254.05	$254.00
Purchase #4	$249.91	8.717%	$271.6947	$271.69	$271.70	$271.70
Purchase #5	$188.61	3.291%	$194.8172	$194.82	$194.80	$194.80
Purchase #6	$85.54	4.731%	$89.5869	$89.59	$89.60	$89.60
Purchase #7	$107.65	10.320%	$118.7595	$118.76	$118.75	$118.80
7 purchase totals =	$1,208.28		$1,298.3712	$1,298.38	$1,298.35	$1,298.40