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	$171.76	8.790%	$186.8577	$186.86	$186.85	$186.90
Purchase #2	$140.72	3.419%	$145.5312	$145.53	$145.55	$145.50
Purchase #3	$196.76	8.240%	$212.973	$212.97	$212.95	$213.00
Purchase #4	$73.71	5.278%	$77.6004	$77.60	$77.60	$77.60
Purchase #5	$167.45	10.668%	$185.3136	$185.31	$185.30	$185.30
Purchase #6	$54.82	5.415%	$57.7885	$57.79	$57.80	$57.80
Purchase #7	$196.92	6.456%	$209.6332	$209.63	$209.65	$209.60
7 purchase totals =	$1,002.14		$1,075.6976	$1,075.69	$1,075.70	$1,075.70