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	$223.87	5.294%	$235.7217	$235.72	$235.70	$235.70
Purchase #2	$89.74	8.275%	$97.166	$97.17	$97.15	$97.20
Purchase #3	$213.57	4.712%	$223.6334	$223.63	$223.65	$223.60
Purchase #4	$71.63	9.252%	$78.2572	$78.26	$78.25	$78.30
Purchase #5	$77.79	11.227%	$86.5235	$86.52	$86.50	$86.50
Purchase #6	$173.86	9.317%	$190.0585	$190.06	$190.05	$190.10
Purchase #7	$122.52	9.744%	$134.4583	$134.46	$134.45	$134.50
7 purchase totals =	$972.98		$1,045.8186	$1,045.82	$1,045.75	$1,045.90