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	$93.25	7.497%	$100.241	$100.24	$100.25	$100.20
Purchase #2	$242.68	12.553%	$273.1436	$273.14	$273.15	$273.10
Purchase #3	$73.30	7.135%	$78.53	$78.53	$78.55	$78.50
Purchase #4	$38.70	8.113%	$41.8397	$41.84	$41.85	$41.80
Purchase #5	$43.63	6.713%	$46.5589	$46.56	$46.55	$46.60
Purchase #6	$226.76	11.275%	$252.3272	$252.33	$252.35	$252.30
Purchase #7	$223.31	10.351%	$246.4248	$246.42	$246.40	$246.40
7 purchase totals =	$941.63		$1,039.0652	$1,039.06	$1,039.10	$1,038.90