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	$115.54	10.834%	$128.0576	$128.06	$128.05	$128.10
Purchase #2	$42.96	6.754%	$45.8615	$45.86	$45.85	$45.90
Purchase #3	$71.58	10.405%	$79.0279	$79.03	$79.05	$79.00
Purchase #4	$136.98	5.543%	$144.5728	$144.57	$144.55	$144.60
Purchase #5	$223.36	3.196%	$230.4986	$230.50	$230.50	$230.50
Purchase #6	$142.64	11.848%	$159.54	$159.54	$159.55	$159.50
Purchase #7	$196.76	12.175%	$220.7155	$220.72	$220.70	$220.70
7 purchase totals =	$929.82		$1,008.2739	$1,008.28	$1,008.25	$1,008.30