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	$31.55	4.745%	$33.047	$33.05	$33.05	$33.00
Purchase #2	$105.28	9.445%	$115.2237	$115.22	$115.20	$115.20
Purchase #3	$47.88	9.783%	$52.5641	$52.56	$52.55	$52.60
Purchase #4	$164.86	12.374%	$185.2598	$185.26	$185.25	$185.30
Purchase #5	$63.28	12.141%	$70.9628	$70.96	$70.95	$71.00
Purchase #6	$115.56	10.681%	$127.903	$127.90	$127.90	$127.90
Purchase #7	$201.64	10.738%	$223.2921	$223.29	$223.30	$223.30
7 purchase totals =	$730.05		$808.2525	$808.24	$808.20	$808.30