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	$213.64	7.713%	$230.1181	$230.12	$230.10	$230.10
Purchase #2	$74.51	7.424%	$80.0416	$80.04	$80.05	$80.00
Purchase #3	$16.33	5.732%	$17.266	$17.27	$17.25	$17.30
Purchase #4	$94.35	5.283%	$99.3345	$99.33	$99.35	$99.30
Purchase #5	$198.62	12.192%	$222.8358	$222.84	$222.85	$222.80
Purchase #6	$122.52	4.507%	$128.042	$128.04	$128.05	$128.00
Purchase #7	$218.75	10.488%	$241.6925	$241.69	$241.70	$241.70
7 purchase totals =	$938.72		$1,019.3305	$1,019.33	$1,019.35	$1,019.20