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	$167.49	4.173%	$174.4794	$174.48	$174.50	$174.50
Purchase #2	$82.94	7.678%	$89.3081	$89.31	$89.30	$89.30
Purchase #3	$193.49	8.104%	$209.1704	$209.17	$209.15	$209.20
Purchase #4	$86.54	11.558%	$96.5423	$96.54	$96.55	$96.50
Purchase #5	$34.37	7.595%	$36.9804	$36.98	$37.00	$37.00
Purchase #6	$39.37	9.289%	$43.0271	$43.03	$43.05	$43.00
Purchase #7	$67.38	12.516%	$75.8133	$75.81	$75.80	$75.80
7 purchase totals =	$671.58		$725.3210	$725.32	$725.35	$725.30