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	$39.82	10.697%	$44.0795	$44.08	$44.10	$44.10
Purchase #2	$64.71	4.766%	$67.7941	$67.79	$67.80	$67.80
Purchase #3	$97.34	5.756%	$102.9429	$102.94	$102.95	$102.90
Purchase #4	$138.97	7.853%	$149.8833	$149.88	$149.90	$149.90
Purchase #5	$89.41	7.818%	$96.4001	$96.40	$96.40	$96.40
Purchase #6	$174.91	12.344%	$196.5009	$196.50	$196.50	$196.50
Purchase #7	$118.81	7.279%	$127.4582	$127.46	$127.45	$127.50
7 purchase totals =	$723.97		$785.0590	$785.05	$785.10	$785.10