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	$129.53	10.146%	$142.6721	$142.67	$142.65	$142.70
Purchase #2	$170.27	11.469%	$189.7983	$189.80	$189.80	$189.80
Purchase #3	$74.25	11.719%	$82.9514	$82.95	$82.95	$83.00
Purchase #4	$199.31	13.399%	$226.0155	$226.02	$226.00	$226.00
Purchase #5	$96.27	5.196%	$101.2722	$101.27	$101.25	$101.30
Purchase #6	$149.66	10.333%	$165.1244	$165.12	$165.10	$165.10
Purchase #7	$81.31	9.737%	$89.2272	$89.23	$89.25	$89.20
7 purchase totals =	$900.60		$997.0611	$997.06	$997.00	$997.10