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	$70.52	10.672%	$78.0459	$78.05	$78.05	$78.00
Purchase #2	$16.93	12.207%	$18.9966	$19.00	$19.00	$19.00
Purchase #3	$158.81	5.744%	$167.932	$167.93	$167.95	$167.90
Purchase #4	$213.44	12.566%	$240.2609	$240.26	$240.25	$240.30
Purchase #5	$201.66	3.649%	$209.0186	$209.02	$209.00	$209.00
Purchase #6	$164.98	4.717%	$172.7621	$172.76	$172.75	$172.80
Purchase #7	$233.94	13.225%	$264.8786	$264.88	$264.90	$264.90
7 purchase totals =	$1,060.28		$1,151.8947	$1,151.90	$1,151.90	$1,151.90