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	$58.60	5.488%	$61.816	$61.82	$61.80	$61.80
Purchase #2	$198.75	4.223%	$207.1432	$207.14	$207.15	$207.10
Purchase #3	$46.86	10.553%	$51.8051	$51.81	$51.80	$51.80
Purchase #4	$49.44	9.437%	$54.1057	$54.11	$54.10	$54.10
Purchase #5	$196.70	13.790%	$223.8249	$223.82	$223.80	$223.80
Purchase #6	$98.62	4.524%	$103.0816	$103.08	$103.10	$103.10
Purchase #7	$92.86	4.196%	$96.7564	$96.76	$96.75	$96.80
7 purchase totals =	$741.83		$798.5329	$798.54	$798.50	$798.50