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	$104.60	4.288%	$109.0852	$109.09	$109.10	$109.10
Purchase #2	$152.76	4.123%	$159.0583	$159.06	$159.05	$159.10
Purchase #3	$238.86	4.620%	$249.8953	$249.90	$249.90	$249.90
Purchase #4	$223.66	3.253%	$230.9357	$230.94	$230.95	$230.90
Purchase #5	$57.32	9.257%	$62.6261	$62.63	$62.65	$62.60
Purchase #6	$109.28	8.174%	$118.2125	$118.21	$118.20	$118.20
Purchase #7	$82.28	6.833%	$87.9022	$87.90	$87.90	$87.90
7 purchase totals =	$968.76		$1,017.7153	$1,017.73	$1,017.75	$1,017.70