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	$92.97	7.873%	$100.2895	$100.29	$100.30	$100.30
Purchase #2	$85.70	4.350%	$89.428	$89.43	$89.45	$89.40
Purchase #3	$172.76	13.744%	$196.5041	$196.50	$196.50	$196.50
Purchase #4	$179.27	7.690%	$193.0559	$193.06	$193.05	$193.10
Purchase #5	$91.78	10.430%	$101.3527	$101.35	$101.35	$101.40
Purchase #6	$96.34	7.124%	$103.2033	$103.20	$103.20	$103.20
Purchase #7	$98.36	3.215%	$101.5223	$101.52	$101.50	$101.50
7 purchase totals =	$817.18		$885.3558	$885.35	$885.35	$885.40