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	$130.57	11.852%	$146.0452	$146.05	$146.05	$146.00
Purchase #2	$61.89	3.618%	$64.1292	$64.13	$64.15	$64.10
Purchase #3	$6.67	4.292%	$6.9563	$6.96	$6.95	$7.00
Purchase #4	$190.72	12.479%	$214.5199	$214.52	$214.50	$214.50
Purchase #5	$237.89	3.305%	$245.7523	$245.75	$245.75	$245.80
Purchase #6	$250.30	7.207%	$268.3391	$268.34	$268.35	$268.30
Purchase #7	$66.97	6.218%	$71.1342	$71.13	$71.15	$71.10
7 purchase totals =	$945.01		$1,016.8762	$1,016.88	$1,016.90	$1,016.80