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	$179.29	10.187%	$197.5543	$197.55	$197.55	$197.60
Purchase #2	$179.83	4.230%	$187.4368	$187.44	$187.45	$187.40
Purchase #3	$129.31	12.245%	$145.144	$145.14	$145.15	$145.10
Purchase #4	$105.38	5.562%	$111.2412	$111.24	$111.25	$111.20
Purchase #5	$98.90	8.459%	$107.266	$107.27	$107.25	$107.30
Purchase #6	$43.41	13.353%	$49.2065	$49.21	$49.20	$49.20
Purchase #7	$196.35	13.119%	$222.1092	$222.11	$222.10	$222.10
7 purchase totals =	$932.47		$1,019.9580	$1,019.96	$1,019.95	$1,019.90