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	$135.64	10.113%	$149.3573	$149.36	$149.35	$149.40
Purchase #2	$169.69	6.326%	$180.4246	$180.42	$180.40	$180.40
Purchase #3	$98.57	11.278%	$109.6867	$109.69	$109.70	$109.70
Purchase #4	$78.44	6.111%	$83.2335	$83.23	$83.25	$83.20
Purchase #5	$138.94	9.599%	$152.2769	$152.28	$152.30	$152.30
Purchase #6	$159.95	7.621%	$172.1398	$172.14	$172.15	$172.10
Purchase #7	$157.83	9.511%	$172.8412	$172.84	$172.85	$172.80
7 purchase totals =	$939.06		$1,019.9600	$1,019.96	$1,020.00	$1,019.90