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	$153.52	9.629%	$168.3024	$168.30	$168.30	$168.30
Purchase #2	$63.81	11.256%	$70.9925	$70.99	$71.00	$71.00
Purchase #3	$5.38	7.399%	$5.7781	$5.78	$5.80	$5.80
Purchase #4	$10.30	3.814%	$10.6928	$10.69	$10.70	$10.70
Purchase #5	$44.32	5.242%	$46.6433	$46.64	$46.65	$46.60
Purchase #6	$81.85	10.106%	$90.1218	$90.12	$90.10	$90.10
Purchase #7	$165.32	12.112%	$185.3436	$185.34	$185.35	$185.30
7 purchase totals =	$524.50		$577.8745	$577.86	$577.90	$577.80