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	$148.95	4.573%	$155.7615	$155.76	$155.75	$155.80
Purchase #2	$108.46	10.198%	$119.5208	$119.52	$119.50	$119.50
Purchase #3	$47.47	12.107%	$53.2172	$53.22	$53.20	$53.20
Purchase #4	$226.33	6.359%	$240.7223	$240.72	$240.70	$240.70
Purchase #5	$103.25	6.620%	$110.0852	$110.09	$110.10	$110.10
Purchase #6	$202.33	13.415%	$229.4726	$229.47	$229.45	$229.50
Purchase #7	$96.82	12.460%	$108.8838	$108.88	$108.90	$108.90
7 purchase totals =	$933.61		$1,017.6634	$1,017.66	$1,017.60	$1,017.70