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	$115.83	10.129%	$127.5624	$127.56	$127.55	$127.60
Purchase #2	$192.90	9.768%	$211.7425	$211.74	$211.75	$211.70
Purchase #3	$196.75	13.310%	$222.9374	$222.94	$222.95	$222.90
Purchase #4	$43.61	10.381%	$48.1372	$48.14	$48.15	$48.10
Purchase #5	$152.95	6.439%	$162.7985	$162.80	$162.80	$162.80
Purchase #6	$47.98	4.745%	$50.2567	$50.26	$50.25	$50.30
Purchase #7	$105.44	12.621%	$118.7476	$118.75	$118.75	$118.70
7 purchase totals =	$855.46		$942.1823	$942.19	$942.20	$942.10