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	$99.39	4.820%	$104.1806	$104.18	$104.20	$104.20
Purchase #2	$70.26	3.284%	$72.5673	$72.57	$72.55	$72.60
Purchase #3	$93.84	5.281%	$98.7957	$98.80	$98.80	$98.80
Purchase #4	$136.94	3.769%	$142.1013	$142.10	$142.10	$142.10
Purchase #5	$236.50	11.760%	$264.3124	$264.31	$264.30	$264.30
Purchase #6	$248.81	11.231%	$276.7539	$276.75	$276.75	$276.80
Purchase #7	$187.81	6.613%	$200.2299	$200.23	$200.25	$200.20
7 purchase totals =	$1,073.55		$1,158.9411	$1,158.94	$1,158.95	$1,159.00