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	$6.92	6.202%	$7.3492	$7.35	$7.35	$7.30
Purchase #2	$55.26	7.297%	$59.2923	$59.29	$59.30	$59.30
Purchase #3	$56.33	5.161%	$59.2372	$59.24	$59.25	$59.20
Purchase #4	$250.86	6.116%	$266.2026	$266.20	$266.20	$266.20
Purchase #5	$122.40	4.172%	$127.5065	$127.51	$127.50	$127.50
Purchase #6	$19.70	3.516%	$20.3927	$20.39	$20.40	$20.40
Purchase #7	$249.36	7.725%	$268.6231	$268.62	$268.60	$268.60
7 purchase totals =	$760.83		$808.6036	$808.60	$808.60	$808.50