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	$59.61	10.604%	$65.931	$65.93	$65.95	$65.90
Purchase #2	$115.69	6.471%	$123.1763	$123.18	$123.20	$123.20
Purchase #3	$178.66	8.458%	$193.7711	$193.77	$193.75	$193.80
Purchase #4	$185.36	7.123%	$198.5632	$198.56	$198.55	$198.60
Purchase #5	$219.59	9.624%	$240.7233	$240.72	$240.70	$240.70
Purchase #6	$249.82	5.444%	$263.4202	$263.42	$263.40	$263.40
Purchase #7	$102.91	8.450%	$111.6059	$111.61	$111.60	$111.60
7 purchase totals =	$1,111.64		$1,197.1910	$1,197.19	$1,197.15	$1,197.20