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	$180.40	4.445%	$188.4188	$188.42	$188.40	$188.40
Purchase #2	$183.75	5.589%	$194.0198	$194.02	$194.00	$194.00
Purchase #3	$87.28	3.263%	$90.1279	$90.13	$90.15	$90.10
Purchase #4	$129.77	10.157%	$142.9507	$142.95	$142.95	$143.00
Purchase #5	$183.52	3.122%	$189.2495	$189.25	$189.25	$189.20
Purchase #6	$184.51	6.687%	$196.8482	$196.85	$196.85	$196.80
Purchase #7	$151.95	8.384%	$164.6895	$164.69	$164.70	$164.70
7 purchase totals =	$1,101.18		$1,166.3044	$1,166.31	$1,166.30	$1,166.20