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	$130.73	9.156%	$142.6996	$142.70	$142.70	$142.70
Purchase #2	$72.50	11.839%	$81.0833	$81.08	$81.10	$81.10
Purchase #3	$132.87	10.142%	$146.3457	$146.35	$146.35	$146.30
Purchase #4	$218.50	11.418%	$243.4483	$243.45	$243.45	$243.40
Purchase #5	$173.94	13.204%	$196.907	$196.91	$196.90	$196.90
Purchase #6	$110.57	3.359%	$114.284	$114.28	$114.30	$114.30
Purchase #7	$79.61	3.212%	$82.1671	$82.17	$82.15	$82.20
7 purchase totals =	$918.72		$1,006.9350	$1,006.94	$1,006.95	$1,006.90