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	$92.31	7.181%	$98.9388	$98.94	$98.95	$98.90
Purchase #2	$108.40	7.278%	$116.2894	$116.29	$116.30	$116.30
Purchase #3	$164.49	5.819%	$174.0617	$174.06	$174.05	$174.10
Purchase #4	$36.42	11.613%	$40.6495	$40.65	$40.65	$40.60
Purchase #5	$50.69	7.361%	$54.4213	$54.42	$54.40	$54.40
Purchase #6	$50.33	7.402%	$54.0554	$54.06	$54.05	$54.10
Purchase #7	$167.68	7.564%	$180.3633	$180.36	$180.35	$180.40
7 purchase totals =	$670.32		$718.7794	$718.78	$718.75	$718.80