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	$135.86	13.372%	$154.0272	$154.03	$154.05	$154.00
Purchase #2	$137.99	3.605%	$142.9645	$142.96	$142.95	$143.00
Purchase #3	$60.33	7.843%	$65.0617	$65.06	$65.05	$65.10
Purchase #4	$223.29	13.489%	$253.4096	$253.41	$253.40	$253.40
Purchase #5	$48.70	11.540%	$54.32	$54.32	$54.30	$54.30
Purchase #6	$174.47	3.844%	$181.1766	$181.18	$181.20	$181.20
Purchase #7	$160.39	5.159%	$168.6645	$168.66	$168.65	$168.70
7 purchase totals =	$941.03		$1,019.6241	$1,019.62	$1,019.60	$1,019.70