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	$159.87	4.685%	$167.3599	$167.36	$167.35	$167.40
Purchase #2	$226.82	12.828%	$255.9165	$255.92	$255.90	$255.90
Purchase #3	$19.89	6.618%	$21.2063	$21.21	$21.20	$21.20
Purchase #4	$103.36	10.222%	$113.9255	$113.93	$113.95	$113.90
Purchase #5	$189.43	10.658%	$209.6194	$209.62	$209.60	$209.60
Purchase #6	$77.90	5.453%	$82.1479	$82.15	$82.15	$82.10
Purchase #7	$167.53	7.581%	$180.2304	$180.23	$180.25	$180.20
7 purchase totals =	$944.80		$1,030.4059	$1,030.42	$1,030.40	$1,030.30