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	$95.52	8.416%	$103.559	$103.56	$103.55	$103.60
Purchase #2	$29.27	3.518%	$30.2997	$30.30	$30.30	$30.30
Purchase #3	$147.82	4.260%	$154.1171	$154.12	$154.10	$154.10
Purchase #4	$13.54	4.539%	$14.1546	$14.15	$14.15	$14.20
Purchase #5	$54.93	13.645%	$62.4252	$62.43	$62.45	$62.40
Purchase #6	$147.25	5.111%	$154.7759	$154.78	$154.80	$154.80
Purchase #7	$97.55	3.416%	$100.8823	$100.88	$100.90	$100.90
7 purchase totals =	$585.88		$620.2138	$620.22	$620.25	$620.30