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	$62.70	10.500%	$69.2835	$69.28	$69.30	$69.30
Purchase #2	$142.48	11.663%	$159.0974	$159.10	$159.10	$159.10
Purchase #3	$185.25	3.187%	$191.1539	$191.15	$191.15	$191.20
Purchase #4	$116.32	6.421%	$123.7889	$123.79	$123.80	$123.80
Purchase #5	$155.36	8.174%	$168.0591	$168.06	$168.05	$168.10
Purchase #6	$157.51	4.499%	$164.5964	$164.60	$164.60	$164.60
Purchase #7	$35.53	11.544%	$39.6316	$39.63	$39.65	$39.60
7 purchase totals =	$855.15		$915.6108	$915.61	$915.65	$915.70