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	$148.48	6.627%	$158.3198	$158.32	$158.30	$158.30
Purchase #2	$141.66	4.521%	$148.0644	$148.06	$148.05	$148.10
Purchase #3	$162.37	8.595%	$176.3257	$176.33	$176.35	$176.30
Purchase #4	$134.66	8.823%	$146.5411	$146.54	$146.55	$146.50
Purchase #5	$166.62	3.780%	$172.9182	$172.92	$172.90	$172.90
Purchase #6	$18.76	7.188%	$20.1085	$20.11	$20.10	$20.10
Purchase #7	$211.78	11.411%	$235.9462	$235.95	$235.95	$235.90
7 purchase totals =	$984.33		$1,058.2239	$1,058.23	$1,058.20	$1,058.10