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	$220.74	7.186%	$236.6024	$236.60	$236.60	$236.60
Purchase #2	$176.66	8.749%	$192.116	$192.12	$192.10	$192.10
Purchase #3	$235.73	5.451%	$248.5796	$248.58	$248.60	$248.60
Purchase #4	$54.91	8.611%	$59.6383	$59.64	$59.65	$59.60
Purchase #5	$31.95	6.169%	$33.921	$33.92	$33.90	$33.90
Purchase #6	$118.74	10.782%	$131.5425	$131.54	$131.55	$131.50
Purchase #7	$142.78	3.473%	$147.7387	$147.74	$147.75	$147.70
7 purchase totals =	$981.51		$1,050.1385	$1,050.14	$1,050.15	$1,050.00