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	$201.27	5.299%	$211.9353	$211.94	$211.95	$211.90
Purchase #2	$144.92	10.657%	$160.3641	$160.36	$160.35	$160.40
Purchase #3	$231.76	4.712%	$242.6805	$242.68	$242.70	$242.70
Purchase #4	$81.93	3.163%	$84.5214	$84.52	$84.50	$84.50
Purchase #5	$39.91	13.447%	$45.2767	$45.28	$45.30	$45.30
Purchase #6	$192.58	12.174%	$216.0247	$216.02	$216.00	$216.00
Purchase #7	$94.49	6.507%	$100.6385	$100.64	$100.65	$100.60
7 purchase totals =	$986.86		$1,061.4412	$1,061.44	$1,061.45	$1,061.40