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	$109.31	13.370%	$123.9247	$123.92	$123.90	$123.90
Purchase #2	$196.72	5.522%	$207.5829	$207.58	$207.60	$207.60
Purchase #3	$77.75	8.343%	$84.2367	$84.24	$84.25	$84.20
Purchase #4	$54.27	3.840%	$56.354	$56.35	$56.35	$56.40
Purchase #5	$44.33	3.566%	$45.9108	$45.91	$45.90	$45.90
Purchase #6	$205.70	8.250%	$222.6703	$222.67	$222.65	$222.70
Purchase #7	$245.74	8.735%	$267.2054	$267.21	$267.20	$267.20
7 purchase totals =	$933.82		$1,007.8848	$1,007.88	$1,007.85	$1,007.90