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	$219.97	10.862%	$243.8631	$243.86	$243.85	$243.90
Purchase #2	$177.72	12.668%	$200.2336	$200.23	$200.25	$200.20
Purchase #3	$68.46	5.118%	$71.9638	$71.96	$71.95	$72.00
Purchase #4	$54.93	9.720%	$60.2692	$60.27	$60.25	$60.30
Purchase #5	$53.90	10.362%	$59.4851	$59.49	$59.50	$59.50
Purchase #6	$194.60	9.820%	$213.7097	$213.71	$213.70	$213.70
Purchase #7	$136.38	6.403%	$145.1124	$145.11	$145.10	$145.10
7 purchase totals =	$905.96		$994.6369	$994.63	$994.60	$994.70