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	$83.36	7.409%	$89.5361	$89.54	$89.55	$89.50
Purchase #2	$245.40	6.225%	$260.6762	$260.68	$260.70	$260.70
Purchase #3	$147.65	5.548%	$155.8416	$155.84	$155.85	$155.80
Purchase #4	$49.38	12.310%	$55.4587	$55.46	$55.45	$55.50
Purchase #5	$202.90	3.532%	$210.0664	$210.07	$210.05	$210.10
Purchase #6	$181.56	4.248%	$189.2727	$189.27	$189.25	$189.30
Purchase #7	$107.51	8.260%	$116.3903	$116.39	$116.40	$116.40
7 purchase totals =	$1,017.76		$1,077.2420	$1,077.25	$1,077.25	$1,077.30