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	$92.50	3.853%	$96.064	$96.06	$96.05	$96.10
Purchase #2	$97.29	12.112%	$109.0738	$109.07	$109.05	$109.10
Purchase #3	$94.73	6.824%	$101.1944	$101.19	$101.20	$101.20
Purchase #4	$52.33	3.370%	$54.0935	$54.09	$54.10	$54.10
Purchase #5	$199.46	12.430%	$224.2529	$224.25	$224.25	$224.30
Purchase #6	$174.70	8.254%	$189.1197	$189.12	$189.10	$189.10
Purchase #7	$154.32	9.315%	$168.6949	$168.69	$168.70	$168.70
7 purchase totals =	$865.33		$942.4932	$942.47	$942.45	$942.60